In-depth practical guides

Calculate and compare a file’s SHA-256 digest

Check whether files retain the same bytes and generate a local integrity record without sending documents to this site.

Updated :

Shelves in Ifremer photographic archives, photographed by Stephane Lesbats.

Shelves in Ifremer photographic archives, photographed by Stephane Lesbats. Documentary context photograph; it does not depict an Alexis Roux ZG assignment or equipment. © Stephane Lesbats / Ifremer · Source · CC BY 4.0. Resized and converted to WebP; cropped display.

Is the received file identical to the preserved one?

Matching names, sizes or appearance are insufficient. SHA-256 is computed from file bytes and helps identify a record or detect change. It proves neither author, creation time nor factual truth. The tool reads only files selected in your browser.

  1. Select the exact record

    Use the preserved original. Printing to PDF, exporting or recompressing an image can preserve meaning while changing bytes. Compare equivalent objects.

  2. Establish the reference

    Use a digest from an identified source or calculate the first file’s digest. Agreement between a document and a digest from the same unverified sender does not establish trustworthy provenance.

  3. Calculate and compare

    The tool accepts up to 64 MiB per file, an expected digest and an optional second file. Calculation requires JavaScript and Web Crypto in a secure context, with no upload.

  4. Keep the record

    Export JSON with algorithm, names, sizes, digests and calculation time. Link it to collection URL, author and date. File names and local modification times are reported metadata.

  5. Interpret differences

    Different digests mean different bytes. Investigate transformation, version or mistaken selection rather than assuming forgery. Use a local tool such as Get-FileHash with SHA256 for larger files.

Compare files locally

SHA-256 calculation in your browser, without upload. Maximum: 64 MiB per file. Time and metadata come from your device, without certification.

64 hexadecimal characters. Keep the reference’s origin separately.

Select a file to start.

Situations and decisions

Typical situations for preparing a check. They do not describe completed assignments or actual observations.

Renamed file

Renaming alone does not change the content digest. Keep both names and check the selected object.

Re-exported PDF

Pagination or metadata may change on export. Digests can differ while the quoted passage appears unchanged; compare text and version.

Digest supplied with the document

Agreement checks consistency between digest and file. Sender identity and document origin need separate checks.

Record to retain

  • SHA-256 algorithm, digest, name and byte size.
  • Expected digest and its source where available.
  • Collection date separate from local calculation time.
  • Known transformation, comparison result and record.

Official references

Related source profiles

Related protocols

Checks before reaching a conclusion

  • Does the expected digest have an identifiable source?
  • Are collection and calculation times distinct?
  • Are differences investigated without automatic accusations?

Frequently asked questions

Is the file sent to the server?

No. Calculation reads locally. The JSON record downloads to your device on request.

Does an equal digest prove truth?

No. It concerns compared bytes. Author, context and content need separate verification.

Why a size limit?

This Web Crypto calculation uses an in-memory buffer. The 64 MiB limit avoids loading large files; use a local tool for larger objects.