This prospectus relates to the resale from time to time by the selling stockholder identified in this prospectus or its permitted transferees (collectively, the “Selling Stockholder”) of up to 4,194,876 shares of Class A Common Stock, par value $0.0001 per share (the “Common Stock”), of Backblaze, Inc. (the “Company,” “Backblaze,” “we,” “our,” or “us”). The shares of Common Stock registered hereunder consist of: (i) 3,053,314 shares of Common Stock (the “Initial Warrant Shares”) issuable upon exercise of a Common Stock Purchase Warrant issued to CoreWeave, Inc. (“CoreWeave”) on June 16, 2026 at an exercise price of $7.60 per share, expiring June 16, 2032 (the “Initial Warrant”); and (ii) 1,141,562 shares of Common Stock (the “Additional Warrant Shares” and, together with the Initial Warrant Shares, the “Warrant Shares”) issuable upon exercise of a Common Stock Purchase Warrant issued to CoreWeave on June 16, 2026 at an exercise price of $7.60 per share, expiring June 16, 2035 (the “Additional Warrant” and, together with the Initial Warrant, the “Warrants”).

Our registration of the Warrant Shares covered by this prospectus does not mean that either we or the Selling Stockholder will issue, offer, or sell, as applicable, any of the Warrant Shares hereby registered. The Selling Stockholder may offer, sell, or distribute all or a portion of the Warrant Shares hereby registered publicly or through private transactions at prevailing market prices or at negotiated prices. The Selling Stockholder may sell the Warrant Shares to or through underwriters, broker-dealers, or agents, who may receive compensation in the form of discounts, concession or commissions from the Selling Stockholder, the purchasers of the Warrant Shares, or both.

We will not receive any of the proceeds from the sale of the Warrant Shares covered by this prospectus. We may, however, receive proceeds from the cash exercise, if any, of the Warrants at $7.60 per share, which we intend to use for working capital and general corporate purposes. We will bear all costs, expenses, and fees in connection with the registration of the Warrant Shares, including compliance with state securities or “blue sky” laws. The Selling Stockholder will bear all commissions and discounts attributable to its sale of shares of Common Stock. See “Plan of Distribution” of this prospectus.

This prospectus provides you with only a general description of the Warrant Shares and the manner in which the Selling Stockholder may offer these Securities. Any prospectus supplement may also add, update, or change information contained in this prospectus. We provide more information about how a Selling Stockholder may sell the Warrant Shares in the section titled “Plan of Distribution” appearing elsewhere in this prospectus.

Our Common Stock is listed on the Nasdaq Global Market under the symbol “BLZE.” On August 3, 2026, the last reported sales price of our Common Stock was $15.59 per share.

Investing in our securities involves significant risks. See the section of this prospectus captioned “Risk Factors” beginning on page 6, in any applicable prospectus supplement and in our Securities and Exchange Commission filings that are incorporated by reference herein.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the “SEC”) under the Securities Act of 1933, as amended (the “Securities Act”), using a “shelf” registration process. Under this prospectus, the selling stockholder identified in this prospectus (the “Selling Stockholder”) may, from time to time, offer and sell, in one or more offerings, up to 4,194,876 shares of our Class A common stock as described in this prospectus. We will not receive any proceeds from the sale of shares by the Selling Stockholder, although we may receive proceeds from any cash exercise of the warrants underlying those shares.

This prospectus provides you with a general description of the shares the Selling Stockholder may offer and the manner in which the Selling Stockholder may offer them. To the extent required, we may provide a prospectus supplement or file a post-effective amendment to the registration statement that will contain specific information about the terms of a particular offering, and that may add, update or change information contained in this prospectus, including with respect to the Selling Stockholder. To the extent there is any conflict between the information in this prospectus and any applicable prospectus supplement, you should rely on the information in the prospectus supplement; if any statement in one of those documents is inconsistent with a statement in another document having a later date, the statement in the document having the later date modifies or supersedes the earlier statement.

You should rely only on the information contained in, or incorporated by reference into, this prospectus, any applicable prospectus supplement and any related free writing prospectus. Neither we nor the Selling Stockholder has authorized anyone to provide you with different or additional information, and we and the Selling Stockholder take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. Neither we nor the Selling Stockholder is making an offer to sell, or the solicitation of an offer to buy, any securities other than the securities described in this prospectus, or an offer to sell or the solicitation of an offer to buy securities in any jurisdiction in which, or to any person to whom, it is unlawful to make such an offer or solicitation. This prospectus does not contain all of the information included in the registration statement; for a more complete understanding of the securities offered, you should refer to the registration statement, including its exhibits.

You should not assume that the information contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus, or incorporated by reference herein or therein, is accurate as of any date other than the respective dates thereof, regardless of the time of delivery of this prospectus or any prospectus supplement or any sale of the securities. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus, any applicable prospectus supplement and any related free writing prospectus, together with the documents incorporated by reference herein and the additional information described under “Where You Can Find More Information” and “Incorporation by Reference,” before making your investment decision.

Unless otherwise indicated, information contained in, or incorporated by reference into, this prospectus concerning our business and the industry and markets in which we operate, including our market position, market opportunity and market size, is based on our management's estimates and research, as well as on industry and general publications, surveys and studies conducted by third parties. Our management's estimates are derived from publicly available information, their knowledge of our business and industry, and assumptions based on such information and knowledge, which they believe to be reasonable. While we believe the third-party information is reliable, we have not independently verified it, and its accuracy and completeness are not guaranteed.

Although we are not aware of any misstatements regarding the market and industry data presented in, or incorporated by reference into, this prospectus, these estimates involve risks and uncertainties and are subject to change based on various factors, including those discussed under the heading “Risk Factors” in this prospectus, any applicable prospectus supplement and the documents incorporated by reference. Accordingly, you should not place undue reliance on this information.

Backblaze, the Backblaze logo and our other registered or common law trademarks, service marks and trade names appearing in this prospectus are the property of Backblaze, Inc. This prospectus also contains trademarks, service marks and trade names of other entities, which are the property of their respective owners. Solely for convenience, trademarks, service marks and trade names referred to in this prospectus may appear without the ® or ™ symbols, but such references are not intended to indicate that we will not assert, to the fullest extent under

applicable law, our rights, or the rights of the applicable licensor, to these trademarks, service marks and trade names. We do not intend our use or display of other entities' trademarks, service marks or trade names to imply a relationship with, or endorsement or sponsorship of us by, any other entity.

Unless the context otherwise requires, references in this prospectus to “Backblaze,” the “Company,” “we,” “us,” “our” and similar terms refer to Backblaze, Inc. and its consolidated subsidiaries.

This prospectus and any accompanying prospectus supplement and free writing prospectus, and the documents incorporated by reference into this prospectus and any related prospectus supplement, contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Exchange Act, that are forward-looking and as such are not historical facts. These forward-looking statements include, without limitation, statements regarding our or our management team’s expectations, hopes, beliefs, intentions or strategies regarding the future, projections, forecasts or other characterizations of future events or circumstances, including any underlying assumptions, and are not guarantees of future performance. The words “may,” “will,” “anticipate,” “believe,” “continue,” “could,” “estimate,” “future,” “expect,” “intends,” “might,” “plan,” “possible,” “potential,” “aim,” “strive,” “predict,” “project,” “should,” “would” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking.

These statements are subject to certain risks and uncertainties that could cause actual results, events and developments to differ materially from our historical experience and our present expectations or projections. Given these risks and uncertainties, you should not place undue reliance on these forward-looking statements. We will discuss many of these risks and uncertainties in greater detail in any prospectus supplement under the heading “Risk Factors.” Additional cautionary statements or discussions of risks and uncertainties that could affect our results or the achievement of the expectations described in forward-looking statements may also be contained in the documents we incorporate by reference into this prospectus. Moreover, we operate in a very competitive and rapidly changing environment. New risks and uncertainties emerge from time to time and it is not possible for us to predict all risks and uncertainties that could have an impact on any forward-looking statements contained in this prospectus.

We cannot assure you that the results, events, and circumstances reflected in the forward-looking statements will be achieved or occur, and actual results, events, or circumstances could differ materially from those described in such forward-looking statements. If any of these risks or uncertainties materializes or any of these assumptions prove incorrect, our results could differ materially from the forward-looking statements. All forward-looking statements in this prospectus are current only as of the date on which the statements were made. We do not undertake any obligation (and expressly disclaim any such obligation) to publicly update any forward-looking statement to reflect events or circumstances after the date on which any statement is made or to reflect the occurrence of unanticipated events, except as required by applicable law.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus and any accompanying prospectus supplement, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and such statements should not be read to indicate that such party has conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain, and investors are cautioned not to unduly rely upon these statements.

An investment in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks and uncertainties discussed under the section titled “Risk Factors” in the applicable prospectus supplement, together with all the other information contained or incorporated by reference in this prospectus and the applicable prospectus supplement. You should also consider the risks, uncertainties and assumptions discussed in the section titled “Risk Factors” in our most recent Annual Report on Form 10-K, as updated by our subsequent Quarterly Reports on Form 10-Q and other filings we make with the SEC, which are incorporated by reference into this prospectus in their entirety and which may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future and by information in a prospectus supplement. The risks described in these documents are not the only ones we face. There may be other risks and uncertainties not presently known to us or that we deem immaterial, which could have material adverse effects on our business, results of operations, financial condition or prospects and could result in a partial or complete loss of your investment. When the Selling Stockholder sells shares of Common Stock pursuant to a prospectus supplement, we may include additional risk factors relevant to that offering in the prospectus supplement.

This prospectus relates to the resale of up to 4,194,876 shares of our Common Stock, which represents approximately 6.8% of our outstanding Common Stock as of August 3, 2026.

The Selling Stockholder may sell all, some, or none of the Common Stock registered hereby in the public market, in privately negotiated transactions, or otherwise. Sales of a substantial number of shares of our Common Stock by the Selling Stockholder, or the perception that such sales may occur, could cause the market price of our Common Stock to decline. Even if the Selling Stockholder does not actually sell a substantial number of shares, the public knowledge that shares are available for sale may depress the market price of our Common Stock.

The presence of shares available for resale in the public market may also make it more difficult for us to raise additional capital through future equity offerings on terms favorable to us, or at all, and may impair our ability to pursue strategic transactions.

The Company will not receive any of the proceeds from the sale of the shares of Common Stock by the Selling Stockholder pursuant to this prospectus. The Selling Stockholder will receive all of the proceeds from the sale of the Common Stock registered by this prospectus. For information about the Selling Stockholder, see “Selling Stockholder.” The Selling Stockholder will be responsible for any broker or similar commissions and any legal fees or other costs of the Selling Stockholder, and we will bear all other costs, fees and expenses incurred in effecting the registration of the shares of our Common Stock covered by this prospectus, including (i) all registration and filing fees, (ii) printing expenses, messenger, telephone and delivery expenses, (iii) fees and expenses of our counsel, auditors, and accountants, and (iv) all expenses related to marketing the sale of the shares of our Common Stock.

The Company may, however, receive proceeds upon the cash exercise of the Warrants at $7.60 per share. There can be no assurance that any of the Warrants will be exercised for cash. We intend to use any proceeds we receive from the cash exercise of the Warrants for working capital and general corporate purposes.

The Selling Stockholder, which as used herein includes donees, pledgees, transferees or other successors-in-interest selling shares of Common Stock or interests in shares of Common Stock received after the date of this prospectus from the Selling Stockholder as a gift, pledge, partnership distribution or other transfer, may, from time to time, sell, transfer or otherwise dispose of any or all of their shares of Common Stock or interests in shares of Common Stock on any stock exchange, market or trading facility on which the shares are traded or in private transactions. These dispositions may be at fixed prices, at prevailing market prices at the time of sale, at prices related to the prevailing market price, at varying prices determined at the time of sale, or at negotiated prices.

The Selling Stockholder may use any one or more of the following methods when disposing of shares or interests therein:

The Selling Stockholder may, from time to time, pledge or grant a security interest in some or all of the shares of Common Stock owned by it and, if it defaults in the performance of its secured obligations, the pledgees or secured parties may offer and sell the shares of Common Stock, from time to time, under this prospectus, or under an amendment to this prospectus under Rule 424(b)(3) or other applicable provision of the Securities Act, amending the list of selling stockholders to include the pledgee, transferee or other successors in interest as a selling stockholder under this prospectus. The Selling Stockholder also may transfer the shares of Common Stock in other circumstances, in which case the transferees, pledgees or other successors in interest will be the selling stockholder(s) for purposes of this prospectus.

In connection with the sale of our Common Stock or interests therein, the Selling Stockholder may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the Common Stock in the course of hedging the positions they assume. The Selling Stockholder may also sell shares of our Common Stock short and deliver these securities to close out their short positions, or loan or pledge the Common Stock to broker-dealers that in turn may sell these securities. The Selling Stockholder may also enter into option or other transactions with broker-dealers or other financial institutions or the creation of one or more derivative securities which require the delivery to such broker-dealer or other financial institution of shares offered by this prospectus, which shares such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction).

The aggregate proceeds to the Selling Stockholder from the sale of any Common Stock offered by it will be the purchase price of the Common Stock less discounts or commissions, if any. The Selling Stockholder reserves the right to accept and, together with its agent from time to time, to reject, in whole or in part, any proposed purchase of Common Stock to be made directly or through agents. We will not receive any of the proceeds from this offering. Upon any exercise of the Warrants by payment of cash, however, we will receive the exercise price of Warrants.

The Selling Stockholder also may resell all or a portion of the shares in open market transactions in reliance upon Rule 144 under the Securities Act, provided that they meet the criteria and conform to the requirements of that rule, or another available exemption from the registration requirements under the Securities Act.

The Selling Stockholder and any underwriters, broker-dealers or agents that participate in the sale of the Common Stock or interests therein may be “underwriters” within the meaning of Section 2(a)(11) of the Securities Act (it being understood that the Selling Stockholder shall not be deemed to be underwriters solely as a result of their participation in this offering). Any discounts, commissions, concessions or profit they earn on any resale of the shares may be underwriting discounts and commissions under the Securities Act. Selling stockholders who are “underwriters” within the meaning of Section 2(a)(11) of the Securities Act will be subject to the prospectus delivery requirements of the Securities Act.

To the extent required, the shares of our Common Stock to be sold, the name of the selling stockholder, the respective purchase prices and public offering prices, the names of any agent, dealer or underwriter, and any applicable commissions or discounts with respect to a particular offer will be set forth in an accompanying prospectus supplement or, if appropriate, a post-effective amendment to the registration statement that includes this prospectus.

In order to comply with the securities laws of some states, if applicable, the Common Stock may be sold in these jurisdictions only through registered or licensed brokers or dealers. In addition, in some states the Common Stock may not be sold unless it has been registered or qualified for sale or an exemption from registration or qualification requirements is available and is complied with.

We have advised the Selling Stockholder that the anti-manipulation rules of Regulation M under the Exchange Act may apply to sales of shares in the market and to the activities of the Selling Stockholder and their affiliates. In addition, to the extent applicable, we will make copies of this prospectus (as it may be supplemented or amended from time to time) available to the Selling Stockholder for the purpose of satisfying the prospectus delivery requirements of the Securities Act. The Selling Stockholder may indemnify any broker-dealer that participates in transactions involving the sale of the shares against certain liabilities, including liabilities arising under the Securities Act.

We have agreed to indemnify the Selling Stockholder against liabilities, including liabilities under the Securities Act and state securities laws, relating to the registration of the shares offered by this prospectus.

We have agreed with the Selling Stockholder to use commercially reasonable efforts to cause the registration statement of which this prospectus constitutes a part to become effective and to remain continuously effective until the earlier of: (i) the date on which all of the “Registrable Securities” as such term is defined in the Registration Rights Agreement and included in this prospectus have been resold or otherwise disposed of and (ii) the date on which all of such Registrable Securities have been sold in accordance with Rule 144 under the Securities Act.

This prospectus covers the resale from time to time of up to 4,194,876 shares of Common Stock by the Selling Stockholder.

The Selling Stockholder identified in the table below may from time to time offer and sell under this prospectus any or all of the shares described under the column “Number of Shares of Common Stock Being Offered” in the table below. The table below has been prepared based upon information furnished to us by the Selling Stockholder as of August 3, 2026. The Selling Stockholder identified below may have sold, transferred, or otherwise disposed of some or all of their shares since the date on which the information in the following table is presented in transactions exempt from or not subject to the registration requirements of the Securities Act. Information concerning the Selling Stockholder may change from time to time and, if necessary, we will amend or supplement this prospectus accordingly and as required.

The following table and footnote disclosure following the table sets forth the name of the Selling Stockholder, the nature of any position, office, or other material relationship, if any, that the Selling Stockholder has had within the past three years with us or with any of our predecessors or affiliates, and the number of shares of our Common Stock beneficially owned by the Selling Stockholder before this offering. The number of shares described under the column “Shares of Common Stock Beneficially Owned Before this Offering” for the Selling Stockholder includes all shares of our Common Stock beneficially held by such Selling Stockholder as of August 3, 2026. The number of shares reflected are those beneficially owned, as determined under applicable rules of the SEC, and the information is not necessarily indicative of beneficial ownership for any other purpose.

Under applicable SEC rules, beneficial ownership includes any shares of Common Stock as to which a person has sole or shared voting power or investment power and any shares of Common Stock which the person has the right to acquire within 60 days after August 3, 2026, through the exercise of any option, warrant or right or through the conversion of any convertible security. Unless otherwise indicated in the footnotes to the table below and subject to community property laws where applicable, we believe, based on information furnished to us, that the Selling Stockholder named in this table has sole voting and investment power with respect to the shares indicated as beneficially owned.

We have assumed that all shares of Common Stock reflected in the table as being offered in the offering covered by this prospectus will be sold from time to time in this offering. We cannot provide an estimate as to the number of shares of Common Stock that will be held by the Selling Stockholder upon termination of the offering covered by this prospectus because the Selling Stockholder may offer some, all, or none of their shares of Common Stock being offered in the offering. Information about the Selling Stockholder may change over time. Any changed information will be set forth in an amendment to the registration statement or supplement to this prospectus, to the extent required

As described in the Current Report on Form 8-K filed by the Company on June 23, 2026, which is incorporated herein by reference, the Company has entered into a Master Strategic Agreement with CoreWeave (the “MSA”) pursuant to which the Company will provide CoreWeave with certain cloud storage and data center managed storage services. In connection with the entry into the MSA, the Company issued the Warrants to CoreWeave. The Initial Warrant will vest and become exercisable in twenty equal quarterly installments (5% per quarter) over a five-year period, in each case so long as the MSA remains in effect. The Additional Warrant will vest and become exercisable in tranches as described therein based upon contracted-for storage capacity, up to 100% of the number of the Additional Warrant Shares. In the case of each Warrant, any unvested portion will become fully vested and exercisable immediately prior to a change of control of the Company (as defined in the Warrants) occurring before termination of the MSA, subject to certain conditions and the potential for forfeiture as described in the Warrants. The exercise of the Warrants is also subject to certain limitations on aggregate share ownership after giving effect to such exercise. The Initial Warrant expires on June 16, 2032 and the Additional Warrant expires on June 16, 2035. Concurrently with the issuance of the Warrants, the Company and CoreWeave entered into a Registration Rights Agreement pursuant to which the Company agreed to file a registration statement covering the resale of the Warrant Shares with the SEC no later than 60 days following the date the Warrants were issued, and to use commercially reasonable efforts to cause that registration statement to be declared effective and to keep it effective for the period specified in the Registration Rights Agreement. The Registration Rights Agreement contains customary provisions, including with respect to registration procedures, permitted suspension periods and indemnification, and registration expenses to be borne by the Company, as well as certain sales volume limitations.

Except as described above and in the June 23, 2026 Form 8-K, the Selling Stockholder does not have, and has not had within the past three years, any position, office, or other material relationship with us or with any of our predecessors or affiliates, other than as a result of the ownership of our Common Stock or other securities.

The validity of the securities being offered hereby is being passed upon for us by Bradley Arant Boult Cummings LLP, Nashville, Tennessee.

The financial statements of Backblaze, Inc. as of December 31, 2025, and for the year then ended, incorporated by reference in this prospectus, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report. Such financial statements are incorporated by reference in reliance upon the report of such firm given their authority as experts in accounting and auditing.

The consolidated financial statements of Backblaze, Inc. as of December 31, 2024 and for each of the two years then ended, incorporated by reference in this prospectus, have been so incorporated in reliance on the report of BDO USA, P.C., an independent registered public accounting firm, given on the authority of said firm as experts in accounting and auditing.

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC's website at http://www.sec.gov. Copies of certain information filed by us with the SEC are also available on our website at www.backblaze.com. Information accessible on or through our website is not incorporated herein or a part of this prospectus.

This prospectus is part of a registration statement we filed with the SEC. This prospectus omits some information contained in the registration statement in accordance with SEC rules and regulations. You should review the information and exhibits in the registration statement for further information on us and the securities we are offering. Statements in this prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings. You should review the complete document to evaluate these statements.

The SEC allows us to incorporate by reference much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus is considered to be part of this prospectus. Because we are incorporating by reference future filings with the SEC to the extent set forth herein, this prospectus is continually updated and those future filings may modify or supersede some of the information included or incorporated by reference in this prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus incorporates by reference the documents listed below and any future filings that we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (in each case, other than those documents or the portions of those documents furnished (but not filed) pursuant to Items 2.02 or 7.01 of any Current Report on Form 8-K), until the offering of the securities being registered under this prospectus is terminated or completed:

We will provide without charge to each person, including any beneficial owner, to whom a copy of this prospectus is delivered, upon written or oral request of any such person, a copy of any or all of the documents that have been or may be incorporated by reference into this prospectus at no cost. Any such request may be made in writing or by telephoning us at the following address or telephone number: