FILE TOOL // 041

File Digital Signature Creator

Sign a file with a freshly generated ECDSA key pair, then save the signature, public key, and file digest in one portable verification bundle.

Processed locally in your browser

Choose a file to sign

One file per signature bundle

Drop files here Select one file. Its bytes stay on this device while Web Crypto creates the digest and signature.

FileSizeType

No files selected.

Key curve Bundle label Hash algorithm Output format

Include creation time

Choose files to begin.0 files

How to use File Digital Signature Creator

Select one file. Its bytes stay on this device while Web Crypto creates the digest and signature.
Adjust the options for the report you need.
Select “Create Signature,” review the result, and download the generated file.

What this file tool does

Sign a file with a freshly generated ECDSA key pair, then save the signature, public key, and file digest in one portable verification bundle.

The tool hashes the selected file and signs its exact bytes with a newly generated ECDSA private key. Only the public key is exported; the private key remains non-extractable.

Processing stays on this device. One local file at a time. Web Crypto support is required. The downloaded JSON bundle contains the signature and public key, not the private signing key.

Supported inputs and limits

One local file at a time. Web Crypto support is required. The downloaded JSON bundle contains the signature and public key, not the private signing key.

Input	Any readable file
Signature	ECDSA via Web Crypto
Bundle	UTF-8 JSON
Private key	Non-extractable and not saved

Example and practical tips

Practical example

Sign a release archive before sending it to a colleague. Send the original file and downloaded signature bundle through separate channels when possible.

Tips

Keep the signature bundle beside the exact file version it belongs to.
Renaming the file does not change its bytes, but editing even one byte invalidates the signature.
Use the companion verifier to check the bundle.

Frequently asked questions

How do I digitally sign a file in my browser?

Choose the file, select an ECDSA curve and hash, then create and download the JSON signature bundle.

Does this tool upload my private file?

No. The file is read locally and processed by the browser's Web Crypto API.

Where is the private signing key stored?

It is created as a non-extractable browser key and is not included in the downloaded bundle.

Can this signature prove my legal identity?

No. It proves that the matching private key signed the bytes, but the newly generated key is not tied to a verified identity or certificate.

Why does the signature stop matching after an edit?

A digital signature covers the exact file bytes, so any content change produces a different verification result.

Related file tools

File Digital Signature Verifier File Checksum Verifier Checksum Generator Hash Manifest Generator

File Digital Signature Creator details

Tool number	041
Category	Integrity & Verification
Processing	Local browser operation
Download	Generated report or verification bundle

Browse more file tools

Callfile categories

File Organization & Naming

Rename, clean, sequence, and validate file names.

View all

Archive & Compression

Create, inspect, compress, and extract archives.

View all

Integrity & Verification

Generate checksums, manifests, and signatures.

View all

File Inspection & Analysis

Inspect bytes, headers, MIME types, and entropy.

View all

Folder & Storage Analysis

Analyze folder size, contents, age, and distribution.

View all

File Splitting & Assembly

Split, join, extract, patch, and verify chunks.

View all

File Security & Privacy

Encrypt files and inspect privacy or safety signals.

View all

Backup & Change Tracking

Compare backup sets and detect file changes.

View all