Batch Timestamping Multiple Files

Why Batch Timestamp?

Many workflows produce multiple files that need proof simultaneously — project deliverables, compliance documents, creative portfolios, research datasets, or build artifacts. Timestamping them individually is tedious and expensive. Batch timestamping solves both problems.

Batch operations use the same unified balance as the rest of TimeProof. Scheduled batching is especially economical — files are combined into a single Merkle tree and anchored in one blockchain transaction for 1 credit per file instead of the 2 credits required for instant mode.

How Batch Timestamping Works

File Hashing

When you select multiple files, TimeProof computes a SHA-256 hash for each one individually in your browser. No files are uploaded. Each hash is a unique 64-character fingerprint of that specific file.

Merkle Tree Construction

The individual file hashes are assembled into a Merkle tree — a binary tree structure where each leaf node is a file hash, and each parent node is the hash of its two children. The single hash at the top of the tree is the Merkle root.

        Merkle Root (anchored on-chain)
       /                              \
    Hash(AB)                       Hash(CD)
   /        \                     /        \
Hash(A)   Hash(B)           Hash(C)   Hash(D)
  |          |                 |          |
File A    File B            File C    File D

Blockchain Anchoring

Only the Merkle root is submitted to the Polygon smart contract — one hash, one transaction, regardless of batch size. This is why batch timestamping is efficient: anchoring 1 file and anchoring 1,000 files costs the same gas.

Individual Certificates

Despite sharing a single on-chain anchor, each file receives its own certificate containing a Merkle proof — the chain of intermediate hashes from the file’s leaf to the root. This proof is sufficient to independently verify any single file without knowing about the other files in the batch.

Step-by-Step: Creating a Batch

1. Prepare Your Files

Gather all files you want to timestamp. They can be any type and any size. If you have many files across different folders, consider creating a temporary folder with everything you want to batch.

2. Select Files

In the TimeProof dashboard, drag multiple files onto the timestamp area or use the file browser to select them. The interface shows each file’s name, size, and computed hash.

3. Choose Anchor Mode

Select scheduled or instant for the batch. All files in a single batch must use the same anchor mode. If you need some files anchored immediately and others batched, create two separate submissions.

4. Optional: Enable Legal-Grade

Toggle LG if you need the courtroom-ready evidence package. Legal-Grade uses plan-aware pricing: Starter and Pro charge 50 credits for up to 25 files, then +2 credits per file after 25. Business charges 25 credits for up to 25 files, then +1 credit per file after 25. Enterprise includes Legal-Grade. Because it is charged once per batch, the effective per-file overhead drops as the batch grows.

5. Confirm

Click Confirm to submit. The interface shows a summary: number of files, anchor mode, credits consumed, and LG status. For instant mode, anchoring happens within seconds. For scheduled mode, files are queued for the next batch window.

6. Download Certificates

After anchoring, each file’s certificate is available for download individually. You can also download all certificates as a ZIP archive.

Batch Cost Comparison

Batch Size	Instant	Scheduled	Scheduled + LG
5 files	10 credits	5 credits	55 credits
25 files	50 credits	25 credits	75 credits
100 files	200 credits	100 credits	150 credits
500 files	1,000 credits	500 credits	550 credits

Notice how the LG overhead becomes negligible at higher file counts. At 500 files, the default 50-credit upgrade adds only 0.1 credit per file, and Business cuts that in half.

Batch Verification

Each file from a batch is independently verifiable:

Re-hash your file: Compute SHA-256 of the original file
Check the certificate: Confirm the hash matches what’s recorded
Walk the Merkle proof: Follow the proof path from the file hash to the Merkle root
Verify on-chain: Look up the Merkle root on Polygonscan to confirm it was anchored at the stated time

The verifier does not need the other files from the batch. Each certificate is self-contained.

The ZIP Archive Strategy

For very large collections where individual file certificates aren’t necessary, consider the ZIP approach:

Place all files in a folder
Create a ZIP archive of the entire folder
Timestamp the single ZIP file — 1 credit, 1 certificate

The ZIP’s hash proves the exact contents of the entire collection. To verify any individual file, extract the ZIP and confirm the contents. This costs a single scheduled timestamp credit if you batch the archive as scheduled, or 2 credits if you anchor it instantly.

Organizing Batch Certificates

By Project

project-a/
  deliverables/
    logo-final.ai
    logo-final-cert.pdf
    brochure-v3.pdf
    brochure-v3-cert.pdf

By Date

2026/
  04-April/
    2026-04-11-batch/
      files/
      certificates/

Keep certificates paired with their original files. A certificate is useless without the original file, and a file is unverifiable without its certificate.

Batch Best Practices

Use scheduled mode for large batches — the 50% credit savings versus instant adds up quickly at volume
Timestamp before sharing — batch all deliverables before sending to clients
Set a schedule — weekly or monthly timestamp sessions for new work
Name files clearly — certificates reference file names, so clear names make certificates meaningful years later
Backup certificates — store in at least two locations (local and cloud)
Test verification periodically — pick a random certificate and verify it to confirm your process works

Batch Timestamps (Reference) — cost planning and advanced strategies
Buying Credits — pack options for batch workflows
Legal-Grade Package — adding court-ready proof to batches
Verifying a Timestamp — confirming batch file proofs