How to Check If Two PDFs Are Identical (2026)
Sometimes you don’t need a full diff — just a yes/no answer: are these two PDFs exactly the same? The fastest method isn’t a comparison tool at all. It’s a checksum.
Quick answer: To check if two PDFs are byte-for-byte identical, compare their SHA-256 hashes — matching hashes mean identical files, instantly. But hashes only answer yes/no: to find what differs, use a visual diff tool like DiffPDF (free) or Adobe Acrobat Pro. Note: re-saved or re-exported PDFs often differ in metadata even when the visible content is the same.
Method 1: SHA-256 Hash (Fastest Yes/No)
A hash reduces a file to a fixed fingerprint. Same fingerprint = same bytes, guaranteed for practical purposes.
# macOS / Linux
shasum -a 256 old.pdf new.pdf
# Windows PowerShell
Get-FileHash old.pdf, new.pdf -Algorithm SHA256If the two hashes match, the files are identical — stop here. If not, you know they differ somewhere, but not where. That’s the hash method’s limit.
Method 2: Visual Diff (Find What Changed)
Hashes can’t show you the difference. For that:
- Free: DiffPDF v2.1.3 — highlights every changed word, character, or page region.
- Professional: Acrobat Pro’s Compare Files — formal filtered report (tutorial).
The Metadata Trap
The #1 surprise: two PDFs with visually identical content but different hashes. Causes:
- Creation timestamps embedded on every export.
- Producer strings (“created by X version Y”).
- Unique document IDs regenerated per save.
So: hash for “is this the exact same file?” (download verification, deduplication), visual/text diff for “is the content the same?” (review, QA, audit). They answer different questions — use the right one. Our batch comparison guide covers stripping metadata for clean batch diffs.
Frequently Asked Questions
How can I tell if two PDFs are exactly the same?
Compare SHA-256 hashes (shasum -a 256 on Mac/Linux, Get-FileHash on Windows). Matching hashes = byte-for-byte identical. This is instant and definitive for the yes/no question.
Why do identical-looking PDFs have different hashes?
Embedded metadata: creation timestamps, producer strings, and unique document IDs change on every export even when visible content is unchanged. Use visual/text diff — not hashes — to compare content.
Hash vs diff tool: which should I use?
Hash when you need a fast yes/no (integrity check, duplicate detection). Diff tool when you need to see and understand the differences (review, QA, audit).
Last updated: October 2026. diffpdf.org is an independent resource center, not affiliated with Qtrac Ltd.