Should I timestamp the zip or every file inside it?

For a formal delivery, the zip (or an equivalent single archive) is usually enough, if that is exactly what you send. If a few files will be used separately, you can date those as well. One TimeBind can hold up to 10 files.

The client says the files they have are different. What now?

Hash both copies. If they differ, they are different files — even when they look the same on screen. Then compare against the dated pack you kept. See how to tell if a file has been changed.

Does a download receipt prove they received the right version?

It can show that someone used the link. Combined with a dated pack, that is much stronger than a receipt alone. It still may not identify *who* downloaded the files.

Can I use the same process for files the client sends me?

Yes. Save exactly what arrived, date it if you may need to show what you were given, and do not mix it with your later edits.

Is this only for paid work?

No. Competition entries, tender uploads and publisher submissions benefit from the same frozen, dated pack. See design competition entry: timestamp before you submit.

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Sending large files to clients safely and keeping proof of what you sent

Inna Hall

November 14, 2026

Guides

Flat illustration of a tablet with a floor plan, rolled blueprints and an outgoing email to a client, with a timestamp badge

Raw video, photo sets, CAD exports, mixed-resolution design packs and stems are often too large for ordinary email. You need a transfer method the client can actually open, and you need a copy of what left your desk. Those are different jobs. A transfer link shows that you sent something, and sometimes who downloaded it. A TimeBind is a dated, checkable record that an exact file existed no later than a recorded time and still matches. The fingerprint is made in the browser, and the file stays on your device. It does not show that the client received the pack, and a download receipt does not, by itself, show that the file they now have is the one you sent.

Some links to other tools on this page are affiliate links, marked “affiliate link”. If you buy through one, TimeBinder may earn a commission, at no extra cost to you. Tools are chosen on merit, with caveats. See our affiliate disclosure.

Why “I emailed it” often fails later
A delivery routine you can repeat
How to send large files without making the client’s life harder
What “proof of what you sent” should look like
Mistakes that leave you arguing about the wrong file
Frequently Asked Questions

Why “I emailed it” often fails later

Disputes about deliveries are rarely about whether a file was sent. They are about which version, which folder, and whether the copy in someone’s archive is still that file.

Typical gaps:

The email has a link that has expired, or that pointed at a folder you later updated.
The client downloaded a later re-export and both of you now call it “the final pack”.
A WeTransfer-style link, a chat attachment, or a shared Drive folder was overwritten after the due date.
The only record is a screenshot of a progress bar.

File-system dates will not settle this. They change when a file is copied or zipped. See what happens to file dates when you copy, zip or download and can a file’s date created be changed?.

What holds up better is a frozen pack — a zip or a clearly named folder of exports — plus a dated fingerprint of that exact pack, plus whatever transfer receipt the sending tool gives you.

A delivery routine you can repeat

Use the same steps for a design presentation, a photo gallery, a music delivery, a planning issue, or a freelance code handoff.

Build a delivery folder, not a live project folder. Export the PDFs, media, or builds you intend the client to have. Leave working files, caches and unused takes out unless they were requested.
Name the pack as a version. project-client-delivery-2026-11-11.zip is easier to find in a year than final-final-2.zip.
Freeze it. Once you have zipped or exported the pack, do not add late files into that same archive and pretend it is the same delivery.
Record the exact pack. Fingerprint the zip (or the small set of files) with TimeBinder before you send it. One TimeBind can hold up to 10 files. Click here to start. Step-by-step help is in how to timestamp a file.
Send a copy, not the only copy. Use a transfer tool, a client portal, or a project workspace. Keep your dated original where you will still have it if the link dies.
Keep the transfer record. Download confirmations, expiry dates, recipient addresses, and any password you set belong in the same job folder as the certificate.
If you send a corrected pack, treat it as a new version. Date it again. Note what changed in a short text file you keep with it.

Architects and designers can pair this with protecting a design before sending it to a client. Musicians can use protect your music before sending and session musician stems before sending. Developers have a close cousin in freelance code delivery before payment.

How to send large files without making the client’s life harder

A good transfer is boring: the client clicks a link, the files arrive complete, and nobody has to create an account if they do not want to.

Practical checks, whatever tool you use:

Size and expiry. If a free plan caps a transfer, or a link dies in a few days, say so in the email and keep your own copy.
A password or a limited link when the pack is unpublished, commercially sensitive, or contains client data. Send the password through a different channel from the link.
A format the client can open. A raw camera pack or a Revit model may need a PDF or IFC companion if the other side does not have the software.
No silent updates. If you use a shared folder that stays open, the folder you pointed at on Monday may not be the folder they download on Friday. For a formal delivery, a dated zip is clearer than a live folder.
A short packing list in the email: file names, version, and what is excluded.

End-to-end encryption, two-factor authentication on your sender account, and virus scanning are worth having when a tool offers them. They protect the journey. They still do not date the bytes.

If you already have a client gallery, a BIM common data environment, or a formal transmittal process, use it. Add a TimeBind of the pack you issued, rather than inventing a second delivery path. For BIM version history compared with a timestamp, see BIM CDE version history vs a timestamp.

Tools that can help with large-file transfer

A transfer tool moves a copy to the client and may keep a download log. It is not a dated fingerprint of the pack, and links can expire. Check current limits and security options on the official site.

Filemail — a large-file transfer service that sends files by email or a shareable link. The official site currently says you can send up to 5 GB free without registration, and that paid plans can send files of any size. Recipients can download without creating an account. Official features include a trackable download link, optional password protection, virus scanning, and, on paid plans, end-to-end encryption and two-factor authentication. How long a link remains available depends on the plan — check current terms. A Filemail receipt shows that a transfer was created and, if you use tracking, whether it was downloaded. It does not, by itself, show that a file the client still has months later is the exact pack you dated.
Proton Drive (affiliate link) — end-to-end encrypted cloud storage that can also share a file or folder with a link. Official materials describe password protection and expiry dates on share links, and say a paid plan is needed to share files over 5 GB. A share link is not a dated fingerprint of the pack you sent, and links can be revoked or expire. Confirm current size and plan limits on the official site. (Proton’s affiliate terms limit promotion to web content; this mention is on a web page only.)

A client portal, a project CDE, a registered transmittal, or another transfer service you already use is a valid non-affiliate option. TimeBinder does not send the file for you. For everyday sync and backup of working files, see secure cloud backup and versioning for creative files.

What “proof of what you sent” should look like

Keep a small, dull pack for each formal delivery:

The exact zip or files you sent (never overwritten).
The TimeBind certificate for that pack.
The transfer receipt or transmittal (link, time, recipient, expiry).
The packing list or covering email.
If the client later approves a version, the approval mail or signed PDF — dated separately if it is a new file. See e-signing contracts, NDAs and split sheets when a signature is involved.

Later, anyone can check a copy against the fingerprint with the SHA-256 hash checker or the file comparison checker. A match shows it is the same file. It does not show that the client opened it, agreed to it, or that you own the work. For the wider method, see how to prove a file existed before a date.

This routine fits the creator and architecture hubs, and it is the same idea on the developer side when you hand over a build.

Mistakes that leave you arguing about the wrong file

Sending a live shared folder and calling it the delivery. Date a frozen export instead.
Replacing files inside a zip you already timestamped. That is a new pack.
Letting the only copy live on an expiring link.
Timestamping the working project instead of the delivered export. The client did not receive your .psd with 40 hidden layers, or they did — be precise.
Assuming a “delivered” tick in a chat app identifies the bytes. Keep the file.

Your file’s fingerprint, anchored to a global network secured by real electricity and cryptography.

Editing a file—including with AI—changes its fingerprint, not its existing network record.

How this works

Your file’s SHA-256 fingerprint, a short code worked out from its exact contents, is made in your browser, and the file itself stays on your device. A cryptographic commitment to that fingerprint, which may be combined with others, is then anchored in a block on the Bitcoin blockchain. Bitcoin is secured by proof of work: computers around the world spend real electricity to add each block, and changing an earlier block would mean redoing that work faster than the rest of the network. Until that block is confirmed, your proof is pending. Once the Bitcoin anchoring is confirmed, you can verify the proof against that recorded commitment. The confirmed record can then be checked; Pooled TimeBinds are checked through TimeBinder, while ASAP TimeBinds can also be checked independently. If you check the file later and its fingerprint still matches, that shows the file existed no later than the recorded time. The record doesn’t show who made the file, whether AI was used, or that its contents are true.

Your filestays on your device
FingerprintSHA-256
Network timestampon Bitcoin

Frequently Asked Questions

Should I timestamp the zip or every file inside it?

For a formal delivery, the zip (or an equivalent single archive) is usually enough, if that is exactly what you send. If a few files will be used separately, you can date those as well. One TimeBind can hold up to 10 files.
The client says the files they have are different. What now?

Hash both copies. If they differ, they are different files — even when they look the same on screen. Then compare against the dated pack you kept. See how to tell if a file has been changed.
Does a download receipt prove they received the right version?

It can show that someone used the link. Combined with a dated pack, that is much stronger than a receipt alone. It still may not identify who downloaded the files.
Can I use the same process for files the client sends me?

Yes. Save exactly what arrived, date it if you may need to show what you were given, and do not mix it with your later edits.
Is this only for paid work?

No. Competition entries, tender uploads and publisher submissions benefit from the same frozen, dated pack. See design competition entry: timestamp before you submit.

Date the pack before you send it

Your first Pooled TimeBind is free, with no credit card required. After that, TimeBinds start from US$5, and an ASAP TimeBind is US$15. Click here to start, or see plans and pricing.

Inna Hall

Inna Hall is an Australian lawyer admitted to the Supreme Court of Queensland and the High Court of Australia in 2013. She has worked across government and private legal practice and is the director of TimeBinder, focusing on document authenticity, evidentiary risk, and blockchain-based proof of existence.