Initializing Secure Environment…
Initializing Secure Environment…
Generate SHA-256, SHA-1, and MD5 cryptographic hash fingerprints for any PDF file to verify integrity, detect tampering, and prove a document has not been altered since a specific point in time. Hashing runs entirely in your browser — no file upload. The fingerprint is unique to the exact byte content of the file: any modification, no matter how small, produces a completely different hash.
This page is about file fingerprints — cryptographic hashes that prove a PDF has not been altered. If you came here looking to make a thumbprint image for a form, use the Thumbmark Maker at ihatepdf.cv/thumbmark-generator instead. To verify that a PDF has not been altered, generate a cryptographic hash of the file and compare it against a known good value. On ihatepdf, drop in the PDF and get its SHA-256, SHA-1 and MD5 fingerprints instantly. If a single byte changes, the hash changes completely — which is how you prove a contract, invoice or evidence file is byte-for-byte the one you were sent. Free, no sign-up, and the file never leaves your device.
In computing, a fingerprint is a short string derived from a file's exact contents — change one byte and the string changes completely — and that is what this page produces. In everyday use, a fingerprint or thumbmark is the ridge pattern on your thumb, which forms and applications sometimes ask you to press onto the page. They share a name because both are meant to identify one thing uniquely, and nothing else. If you are filling in a form that has a box marked "thumbmark", the Thumbmark Maker is the tool you want; it turns a photo of your inked thumb into a clean transparent image. If you are trying to prove a contract has not been edited since you sent it, stay here.
Legal professionals use document hashes to prove a contract or evidence document has not been altered since signing. IT and compliance teams use hashes to verify that distributed policy documents have not been modified in transit. Journalists use hashes to prove source documents are authentic and unmodified. Accountants use hashes to create an audit trail showing financial documents have not been changed after review. The hash value is meaningless on its own — its value comes from comparing it to the hash of the same file at a different point in time.
No — this page generates a cryptographic file fingerprint, which is a string of characters that identifies the exact bytes of a document. If you need an image of your thumbprint to place on a form, that is a different tool: Thumbmark Maker at ihatepdf.cv/thumbmark-generator photographs your inked thumb and cuts it out onto a transparent background.
A hash is a fixed-length string generated from the exact byte content of a file. SHA-256 produces a 64-character string. If even one character in the PDF changes, the hash changes completely. This makes hashes ideal for verifying a document has not been altered.
SHA-256 is recommended for security-sensitive use cases. MD5 and SHA-1 are faster but have theoretical vulnerabilities for adversarial forgery — they are still reliable for simple integrity verification of non-adversarial scenarios.
No. Hashing runs entirely in your browser's memory using the Web Crypto API. The file never leaves your device.
Yes. Generate and record the hash before distribution. If a recipient claims the document was altered, compare the hash of the received file to the original hash. Identical hashes prove the file is unchanged.
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