How accurate is PDF modification detection?
Our PDF modification detection system combines several layers of analysis, from metadata and file structure to digital signatures. How much a result can tell you depends on the file: some documents carry far more evidence than others, which is why there is a third verdict.
Results come in three states: Intact (no signs of modification found), Modified (modification detected), and Inconclusive (the file’s origin can’t vouch for it – for example, a document produced in consumer software that anyone could use to create it from scratch).
There is one fundamental limitation to understand: the tool detects post-creation modifications, not fabricated content. A document whose content was false from the moment it was first produced carries no evidence of later editing, because nothing was changed afterwards. Intact means no modification was detected, not that the document is genuine. The check only tells you whether the file was changed after it was generated, not whether the data inside it is truthful. See Can someone create a fake document from scratch? for details.
For critical decisions, we recommend using this tool as part of a broader fraud-detection strategy rather than relying solely on automated results.
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How Detection Works
HTPBE? looks for evidence inside the file that it was changed after it was created, reports each finding by name, and returns Intact, Modified or Inconclusive. It reads the file, not the text of the document.
No. HTPBE? looks for evidence that an existing PDF was changed after it was created, so content that was false from the start can show none, and password-protected files cannot be analysed. Treat it as one layer in a fraud check.
Privacy, Data & Limits
Files up to 10 MB (10,485,760 bytes) are accepted, in the web app and through the API. Larger files are rejected with an error. Compressing or splitting a file creates a new file, so the verdict describes that copy.