Offer Letter between the Registrant and Stewart Butterfield dated March 7, 2019

Slack Technologies, Inc. (the “Company”) is pleased to confirm the terms of your continued employment, effective as of January 1, 2019:

of the terms of your employment with the Company and supersede any prior agreements, representations or understandings (whether written, oral or implied) between you and the Company. This letter agreement may not be amended or modified, except by an express written agreement signed by both you and a duly authorized officer of the Company (other than you). The terms of this letter agreement and the resolution of any disputes as to the meaning, effect, performance or validity of this letter agreement or arising out of, related to, or in any way connected with, this letter agreement, your employment with the Company or any other relationship between you and the Company (the “Disputes”) will be governed by California law, excluding laws relating to conflicts or choice of law.

You may indicate your agreement with these terms and accept this confirmatory offer of continued employment by signing and dating the enclosed duplicate original of this letter agreement and returning it to me.

As required by law, your employment with the Company is contingent upon your providing legal proof of your identity and authorization to work in the United States.

1.I have not entered into, and I agree I will not enter into, any agreement either written or oral in conflict with this Agreement or my employment with Company. I will not violate any agreement with or rights of any third party or, except as expressly authorized by Company in writing hereafter, use or disclose my own or any third party's confidential information or intellectual property when acting within the scope of my employment or otherwise on behalf of Company. Further, I have not retained anything containing any confidential information of a prior employer or other third party whether or not created by me.

2.Company shall own all right, title and interest (including patent rights, copyrights, trade secret rights, mask work rights, sui generis database rights and all other intellectual property rights of any sort throughout the world) relating to any and all inventions (whether or not patentable), works of authorship, mask works, designs, know­-how, ideas and information made or conceived or reduced to practice, in whole or in part, by me during the term of my employment with Company to and only to the fullest extent allowed by California Labor Code Section 2870 (which is attached as Appendix A) (collectively ''Inventions'') and I will promptly disclose all Inventions to Company. Without disclosing any third party confidential information, I will also disclose anything I believe is excluded by Section 2870 so that the Company can make an independent assessment. I hereby make all assignments necessary to accomplish the foregoing. I shall further assist Company, at Company's expense, to further evidence, record and perfect such assignments, and to perfect, obtain, maintain, enforce, and defend any rights specified to be so owned or assigned. I hereby irrevocably designate and appoint Company as my agent and attorney-in-fact, coupled with an interest and with full power of substitution, to act for and in my behalf to execute and file any document and to do all other lawfully permitted acts to further the purposes of the foregoing with the same legal force and effect as if executed by me. If I wish to clarify that something created by me prior to my employment that relates to Company's actual or proposed business is not within the scope of the foregoing assignment, I have listed it on Appendix B in a manner that does not violate any third party rights or disclose any confidential information. Without limiting Section l or Company's other rights and remedies, if, when acting within the scope of my employment or otherwise on behalf of Company, I use or (except pursuant to this Section 2) disclose my own or any third party's confidential information or intellectual property (or if any Invention cannot be fully made, used, reproduced, distributed and otherwise exploited without using or violating the foregoing), Company will have and I hereby grant

Company a perpetual, irrevocable, worldwide royalty-free, non-exclusive, sublicensable right and license to exploit and exercise all such confidential information and intellectual property rights.

3.To the extent allowed by law, paragraph 2 includes all rights of paternity, integrity, disclosure and withdrawal and any other rights that may be known as or referred to as "moral rights," ''artist's rights," "droit moral," or the like (collectively "Moral Rights"). To the extent I retain any such Moral Rights under applicable law, I hereby ratify and consent to any action that may be taken with respect to such Moral Rights by or authorized by Company and agree not to assert any Moral Rights with respect thereto. I will confirm any such ratifications, consents and agreements from time to time as requested by Company.

4.I agree that all Inventions and all other business, technical and financial information (including, without limitation, the identity of and information relating to customers or employees) I develop, learn or obtain during the term of my employment that relate to Company or the business or demonstrably anticipated business of Company or that are received by or for Company in confidence, constitute "Proprietary Information." I will hold in confidence and not disclose or, except within the scope of my employment, use any Proprietary Information. However, I shall not be obligated under this paragraph with respect to information I can document is or becomes readily publicly available without restriction through no fault of mine. Upon termination of my employment, I will promptly return to Company all items containing or embodying Proprietary Information (including all copies), except that I may keep my personal copies of (i) my compensation records, (ii) materials distributed to shareholders generally and

(iii) this Agreement. I also recognize and agree that I have no expectation of privacy with respect to Company's telecommunications, networking or information processing systems (including, without limitation, stored computer files, email messages and voice messages) and that my activity and any files or messages on or using any of those systems may be monitored at any time without notice.

5.Until one year after the term of my employment, I will not encourage or solicit any employee or consultant of Company to leave Company for any reason (except for the bona fide firing of Company personnel within the scope of my employment).

6.I agree that during the term of my employment with Company (whether or not during business hours), I will not engage in any activity that is in any way competitive with the business or demonstrably anticipated business of Company, and I will not assist any other person or organization in competing or in preparing to compete with any business or demonstrably anticipated business of Company.

7.I agree that this Agreement is not an employment contract for any particular term and that I have the right to resign and Company has the right to terminate my employment at will, at any time, for any or no reason, with or without cause. In addition, this Agreement does not purport to set forth all of the terms and conditions of my employment, and, as an employee of Company, I have obligations to Company which are not set forth in this Agreement. However, the terms of this Agreement govern over any inconsistent terms

and can only be changed by a subsequent written agreement signed by the President of Company.

8.I agree that my obligations under paragraphs 2, 3, 4 and 5 of this Agreement shall continue in effect after termination of my employment, regardless of the reason or reasons for termination, and whether such termination is voluntary or involuntary on my part, and that Company is entitled to communicate my obligations under this Agreement to any future

employer or potential employer of mine. My obligations under paragraphs 2, 3 and 4 also shall be binding upon my heirs, executors, assigns, and administrators and shall inure to the benefit of Company, its subsidiaries, successors and assigns.

9.Any dispute in the meaning, effect or validity of this Agreement shall be resolved in accordance with the laws of the State of California without regard to the conflict of laws provisions thereof. I further agree that if one or more provisions of this Agreement are held to be illegal or unenforceable under applicable California law, such illegal or unenforceable portion(s) shall be limited or excluded from this Agreement to the minimum extent required so that this Agreement shall otherwise remain in full force and effect and enforceable in accordance with its terms. This Agreement is fully assignable and transferable by Company, but any purported assignment or transfer by me is void. I also understand that any breach of this Agreement will cause irreparable harm to Company for which damages would not be an adequate remedy, and, therefore, Company will be entitled to injunctive relief with respect thereto in addition to any other remedies and without any requirement to post bond.

(a)Any provision in an employment agreement which provides that an employee shall assign, or offer to assign, any of his or her rights in an invention to his or her employer shall not apply to an invention that the employee developed entirely on his or her own time without using the employer's equipment, supplies, facilities, or trade secret information except for those inventions that either:

(1)    Relate at the time of conception or reduction to practice of the invention to the employer's business, or actual or demonstrably anticipated research or development of the employer; or

(b)To-the extent a provision in an employment agreement purports to require an employee to assign an invention otherwise excluded from being required to be assigned under subdivision (a), the provision is against the public policy of this state and is unenforceable.