What does a ProofSnap file certification prove?

A ProofSnap file certification is a proof of existence: it shows that a file with exactly this content existed no later than the moment of the timestamp, and it lets anyone check later that the file has not changed, because any change gives the file a different SHA-256 hash.

How many file certifications does each plan include?

Each month, ProofSnap Essential includes 5 file certifications, Professional 15, Enterprise 50 and Company an unlimited number. A regular SnapPack adds 3 file certifications that stay valid for 12 months. One package counts as one certification, however many files it holds, so ten related files certified together use one.

Can I use the certificate in court?

Yes. Before an EU court, the optional qualified eIDAS timestamp carries a presumption that its date and time are accurate and that the data it covers is intact. For a US federal court, the optional declaration template from step 5 can make the files self-authenticating once a qualified person signs it and the adverse party has received written notice. Hand over the original ZIP unchanged. A court decision on a Bitcoin timestamp is summarized on the File Certification page.

Can I certify a file without a subscription?

Yes. A ProofSnap SnapPack is a one-time purchase of $4.99 and includes 3 file certifications, valid for 12 months, plus 10 web page captures. Each file certification carries the Bitcoin timestamp; the qualified eIDAS timestamp needs an eIDAS SnapPack or a Video SnapPack.

I closed the side panel before downloading. Can I get the package back?

No. The package is built in your browser and is not stored on ProofSnap servers, so closing the panel deletes it. Certify the files again and download before you close the panel.

The result says Bitcoin (pending). Did something go wrong?

No, that is the normal state right after certifying. The anchor is submitted and Bitcoin confirms it, usually within a few hours. The ZIP you downloaded needs no changes: when you check it after a few hours, the verifier fetches the Bitcoin confirmation and shows the block. To check the anchor yourself, see how to verify an OpenTimestamps file.

Should I certify ten files in one package or one by one?

Files that belong together, such as all drafts of one design or all documents for one matter, go into one package: one timestamp, one certification. Certify a file on its own when you expect to hand it to someone separately.

Why is the Certify button dimmed, with a red message saying the limit has been reached?

You have used this month's file certifications. The allowance resets on the 1st. To continue now, use Upgrade plan under the message or buy a SnapPack; its file-certification credits kick in after your monthly allowance runs out.

Can I rename the files or the ZIP afterward?

You can rename the ZIP. Leave the files inside it as they are: the manifest refers to them by name, and changing a name or a single byte makes the verifier report the package as modified. The original you keep outside the ZIP can have any name; only its content is compared.

Step-by-step guide

How to certify a file with ProofSnap

To certify a file with ProofSnap in 2026, open the File Certifier in the browser side panel, add your files and click Certify. Your browser hashes each file with SHA-256, and ProofSnap anchors the result in Bitcoin, optionally with an EU qualified timestamp. You download a signed ZIP showing the files existed no later than that moment.

By Radim Motycka, Founder and Lead Engineer at ProofSnap, who built the File Certifier described on this page · Last updated: October 15, 2026

Steps

Nine, all in the side panel

File size

600 MB per file, 1 GB per package

Your file

Hashed in your browser

Before you start

ProofSnap is installed in Google Chrome or Microsoft Edge. Install it here.
You are signed in and have either a subscription plan or SnapPack credits.
The files you want to certify are final. Any later change to a file, even saving it again, gives it a different hash, and the certificate no longer matches it.

New to ProofSnap? Install it first: getting started.

Step 1

Open the ProofSnap side panel

Click the ProofSnap icon in the browser toolbar. The side panel opens on the right side of the window. If you do not see the icon, open the puzzle-piece menu (Extensions) and pin ProofSnap so it stays in the toolbar.

1ProofSnap icon. One click opens the side panel. The File Certifier works on any tab; it does not matter which page you have open.
2Account menu. Shows that you are signed in. If you see the sign-in screen instead, sign in first.
3Language. Switches the language of the whole panel. The certificate language is chosen separately in step 5.
4File Certifier. The File Certifier sits right under the ProofSnap Trust Verifier, near the bottom of the panel.

Step 2

Expand the File Certifier

Scroll to the bottom of the side panel and click File Certifier. The card opens and shows the drop zone.

1Card header. Click it again to collapse the card. The arrow points down while the card is open.
2Monthly allowance. On a subscription with a monthly limit, the bar shows how many certifications you have used this month. It resets on the 1st. With SnapPack credits only, there is no bar. Allowances per plan are compared in how to choose a plan.
3Drop zone. Accepts any file type, including PDFs, images, video, audio, source code, archives and spreadsheets.
4Certify button. Stays dimmed until you add at least one file.

File Certifier

Drop one or more files to certify their existence with a blockchain timestamp.

3/15

Click to upload or drag and drop

Any file type. 600 MB per file, 1 GB per package. Multiple files supported.

Certify File

The allowance shown is an example.

Step 3

Add your files

Click the drop zone and pick files, or drag them onto it from your desktop or a folder. You can add files in several batches; they collect in the list below the drop zone.

1Selected files. Name and size of each file. The list scrolls when it gets long.
2Remove. The X removes a file from the list before you certify.
3Certify button. Now active, and it counts your files: Certify File for one, Certify 3 files for three.

One file or many?

A single file produces a package of its own. Several files are combined into one package with one timestamp, and the certificate PDF lists every file with its own SHA-256 hash. Either way, the package counts as one certification.

There is no limit on the number of files. A single file can be up to 600 MB, and all the files in one package up to 1 GB combined. A file that exceeds either limit is not added; a note above the list names it, and the files that fit stay selected. Split larger sets into several packages.

File Certifier

Drop one or more files to certify their existence with a blockchain timestamp.

3/15

Click to upload or drag and drop

Any file type. 600 MB per file, 1 GB per package. Multiple files supported.

logo-final-v3.ai

14.2 MB

brand-guidelines.pdf

3.8 MB

sketches-2026-10.zip

96.5 MB

Certify 3 files

Example file names. Set the options in steps 4 and 5 before you click Certify.

Step 4 (optional)

Case and examiner details

The options sit below the Certify button. Set them before you click it, because they are written into the package while it is being built. Click Case & examiner details (optional) to open three fields.

1Case / matter reference. Your file number, docket number or internal matter number, up to 120 characters.
2Examiner name. Who performed the certification, up to 120 characters.
3Note. A short context line, up to 500 characters.

What you enter appears on the certificate PDF and in chain_of_custody.json. When you collapse the group, the reference and the examiner name stay visible next to its title, so you can check them at a glance.

Certify 3 files

Case & examiner details (optional)

1Case / matter reference (optional)

Matter #4821

2Examiner name (optional)

Jane Doe, Forensic Examiner

3Note (optional)

Short context for this capture

Court filing forms (optional)

Evidence languageEnglish

Include EU Qualified Timestamp (eIDAS)

8/10

Lower part of the File Certifier card. Example values.

Step 5 (optional)

Court forms, language and the EU qualified timestamp

Below the case details are three more settings. If you are not sure, leave them as they are; the defaults suit most people.

1Court filing forms (optional). Open the group and switch on US self-authentication certification (FRE 902) only when the files go to a US federal court. It adds rule_902_certification.pdf, a declaration template that identifies your files by hash. A qualified person completes and signs it, and your attorney gives the adverse party the written notice the rule requires and files or serves the signed copy (see how to complete the declaration). Leave the copy in the package untouched. The form is always in English and off by default, and ProofSnap remembers your choice.
2Evidence language. The language of the certificate PDF. It defaults to the panel language, and you can pick any of the 29 languages, for example to submit a German-language certificate to an Austrian court while you work in English.
3Include EU Qualified Timestamp (eIDAS). Adds a qualified electronic timestamp from Disig a.s., a Qualified Trust Service Provider on the EU Trusted List, on top of the Bitcoin timestamp. Article 41(2) of the eIDAS Regulation reads: "A qualified electronic time stamp shall enjoy the presumption of the accuracy of the date and the time it indicates and the integrity of the data to which the date and time are bound." The number on the right shows how many qualified timestamps you have left.

Why is my eIDAS switch gray?

The qualified timestamp comes with the Enterprise and Company plans and with an eIDAS SnapPack or a Video SnapPack. Without one of them, the switch is gray and an Upgrade plan link sits next to it. When your qualified timestamps run out, the switch stays visible but cannot be turned on until you add credits.

The Bitcoin timestamp needs no switch. Every file certification gets it on every plan.

Certify 3 files

Case & examiner details (optional)· Matter #4821 · Jane Doe, Forensic Examiner

1Court filing forms (optional)

US self-authentication certification (FRE 902)

Adds an unsworn declaration for US federal court under Federal Rules of Evidence 902(13) and 902(14) that identifies the certified files by hash; you complete and sign it. File the signed copy with the court, not back into the package: changing the file would break the hash values and the package would fail verification. Always in English, because it is a US court filing. Leave the toggle off for non-US courts; your choice is remembered.

2Evidence languageDeutsch

Include EU Qualified Timestamp (eIDAS)

8/10

Without an eIDAS plan or SnapPack

Include EU Qualified Timestamp (eIDAS)Upgrade plan

The counter value is an example.

Step 6

Click Certify and keep the panel open

Scroll back up and click Certify File or Certify 3 files. A spinner and a progress bar appear while ProofSnap works. Small files take seconds; a package close to 1 GB takes longer. Do not close the side panel during this step.

What happens in the background

1Hashing. Your browser computes a SHA-256 hash of every file. The files themselves are not uploaded anywhere.
2Signing. The hashes go into manifest.json, which is signed with a fresh RSA-4096 key. The signature binds the hashes together; the timestamps in the next step make a later change to the files detectable.
3Timestamping. Your files never leave your computer; only the hashes do. The timestamp is applied to the file's own SHA-256 hash for a single file, and to the manifest's hash for several files. ProofSnap's timestamp service passes that hash to the OpenTimestamps calendars for the Bitcoin anchor, and to Disig if you turned on eIDAS. ProofSnap also registers the manifest hash so the verifier can recognize the package.
4Packaging. ProofSnap builds the certificate PDF and puts everything into one ZIP.

If one of your files cannot be read, ProofSnap stops before any timestamp is requested, and nothing is counted against your allowance or credits.

File Certifier

Drop one or more files to certify their existence with a blockchain timestamp.

3/15

Combining 3 files into one package...

logo-final-v3.ai

brand-guidelines.pdf

sketches-2026-10.zip

The files of a combined package move through each stage together.

Step 7

Download the certificate package

When the result card appears, click Download Certificate Package right away.

1Result. How many files were certified. For a single file you also see its name, size and SHA-256 hash.
2Timestamps. Bitcoin (pending) is the normal state: the anchor is submitted and Bitcoin confirms it, usually within a few hours. Qualified (Disig) means the eIDAS timestamp is in the package; Off means you did not switch it on. Unavailable means the service did not respond, and the package was saved without that timestamp.
3Download now. The package exists only in your browser and is not stored on ProofSnap servers. Closing the side panel deletes it for good.
4Download Certificate Package. Saves a ZIP with a name like file-certification-batch-3-files-2026-10-14.zip, or file-certification-contract.pdf-2026-10-14.zip for a single file.
5Certify another file. Clears the card for the next package. Download first.

If a timestamp service does not respond, a gray notice above the button says so and the package is saved without that timestamp.

File Certifier

Drop one or more files to certify their existence with a blockchain timestamp.

4/15

3 files certified

Blockchain: Bitcoin (pending)

eIDAS: Qualified (Disig)

✓logo-final-v3.ai14.2 MB

✓brand-guidelines.pdf3.8 MB

✓sketches-2026-10.zip96.5 MB

3Download now: not stored on our servers

4Download Certificate Package

Certify another file5

One combined package used one certification from the allowance.

Step 8

What is inside the ZIP

Keep the ZIP exactly as you downloaded it. Do not unpack, edit and re-zip it for filing: hand over the original ZIP, and copy files out of it only to read them. To prove a file existed on a date, these are the files that carry the proof (more in how to read an evidence package):

Your files: The certified originals, byte for byte (unusual characters in file names may be normalized). A single file sits at the root of the ZIP; several files sit in the files/ folder.
provenance_certificate.pdf: The certificate to read and print: the files with their SHA-256 hashes, the timestamps requested, your case details and instructions for verifying it. It is in the evidence language you chose.
manifest.json, manifest.sig, publickey.pem: The list of hashes, its RSA-4096 signature and the key to check that signature.
manifest.json.ots: The Bitcoin timestamp (OpenTimestamps). It shows that the files existed no later than the moment of anchoring.
manifest.json.tsr, eidas_validation.json: The EU qualified timestamp and its validation data, when you switched eIDAS on.
chain_of_custody.json, forensic_log.json: Which ProofSnap account certified what, when and in which browser, plus a log of each step from file selection to manifest creation, each entry chained to the previous one by its hash.
verification/: verify.sh for macOS and Linux, verify.ps1 for Windows, and a plain-text guide, so a third party can re-check the hashes and the signature on their own computer.
rule_902_certification.pdf: The US court declaration template, only when you switched it on in step 5.

file-certification-batch-3-files-2026-10-14.zip

files/
logo-final-v3.ai
brand-guidelines.pdf
sketches-2026-10.zip
verification/
verify.sh
verify.ps1
VERIFICATION_GUIDE.txt
provenance_certificate.pdf
manifest.json
manifest.sig
publickey.pem
manifest.json.ots
manifest.json.tsr
eidas_validation.json
chain_of_custody.json
forensic_log.json

Combined package with eIDAS switched on, opened in the file manager.

Step 9

Verify the package later

Wait a few hours after certifying so the Bitcoin anchor can be confirmed. Then anyone can check the package: you in the side panel, or opposing counsel and the court in the ProofSnap Trust Verifier on this website, no account needed. For a check that runs entirely offline, the scripts in the package's verification/ folder re-check the hashes and the signature. Every check is explained in how to verify an evidence package.

1Upload the ZIP. Open the ProofSnap Trust Verifier card above the File Certifier, drop the ZIP, then click Verify zip file.
2Verdict. Integrity: match means the files match the manifest and the manifest matches its signature. Integrity: modified means something in the package was changed or is missing.
3Check the original. For a file certification the verifier also offers Verify original file matches certificate. Drop the original file you kept: File matches certificate confirms it is exactly the file that was certified.
4Show technical verification. Expands the full list of checks: hashes, signature, the Bitcoin block of the anchor, the eIDAS timestamp and the chain of custody.

Verifier in the side panel after verifying the ZIP and dropping one original file. A match shows the file is identical; the timestamp shows it existed no later than the anchored time.

Common questions

Certify your first file

Install ProofSnap, open the side panel and follow the steps above. File certification is part of every ProofSnap plan.

Install ProofSnap, 7 days free

Also available for Microsoft Edge

More about what a certification proves: File Certification