Verify a File Checksum Online Free
✅ Verify a Downloaded File's Checksum
Drop the file below, paste the checksum the publisher gave you, and get an instant match or mismatch verdict. Your file never leaves this tab.
📁 Select a File
🔄 Reading and hashing file — this may take a moment for large files...
🔑 Expected Checksum (optional)
Drop a file to begin
Add an expected checksum to see a match/mismatch verdict, or just view the computed hashes below.
Quick answer: Drop your downloaded file into the box, then paste the checksum the publisher listed on their download page. The tool computes MD5, SHA-1, SHA-256, SHA-384, and SHA-512 for your file using the browser's Web Crypto API, automatically detects which algorithm you pasted by its exact character length, and shows a clear ✅ Match or ❌ Mismatch verdict. No expected hash handy? The computed hashes are listed below regardless, ready to copy. The file is read and hashed entirely on your device - it is never uploaded anywhere.
- Cost: Free, unlimited files, no signup.
- Where it runs: 100% in your browser — the file is never uploaded.
- Algorithms: MD5, SHA-1, SHA-256, SHA-384, SHA-512 — computed together.
- Auto-detection: Algorithm identified from the exact length of your pasted checksum.
- Checksum-file aware: Handles lines like "hash␣␣filename" automatically.
- Verdict, not just output: A clear match/mismatch result, not just raw hex to eyeball.
📦 Large Files Take Memory: The entire file is read into your browser's memory to compute the hash — multi-gigabyte ISO files may take longer or use significant RAM on low-memory devices.
🐢 MD5 Runs in Plain JavaScript: SHA-1 through SHA-512 use your browser's native, hardware-accelerated crypto engine; MD5 isn't part of that API, so it's computed in JavaScript and will be slower on very large files.
✅ Privacy: Your file is read and hashed locally. It is never uploaded, transmitted, or stored anywhere.
✅ 100% Private: Your file is hashed locally using the Web Crypto API and JavaScript. It is never uploaded to a server or stored anywhere.
Note: Nothing is saved — reloading the page clears the selected file and results completely.
How to Verify a File's Checksum
Drop In Your File
Drag and drop the downloaded file, or click to browse for it.
Paste the Expected Checksum
Copy the hash the publisher provided and paste it in.
Read the Verdict
See an instant Match or Mismatch result, with the algorithm auto-detected.
Copy Any Hash
Copy any computed hash if you need it for your own records.
🔒 Your File Never Leaves Your Device
Hashing happens entirely inside your browser tab using the Web Crypto API and JavaScript. There is no upload step, no server-side processing, and no network request that contains your file's contents.
Common Uses for a File Checksum Verifier
OS & Linux Distro ISOs
Confirm an Ubuntu, Debian, or Windows ISO downloaded completely and matches the official image before you burn or boot it.
Software Installers
Verify a vendor's installer against the checksum on their release page before running it.
Open-Source Releases
Check a GitHub release artifact against the SHA-256 sums file the maintainer published alongside it.
Confirming a Clean Transfer
Make sure a file copied over a slow connection or external drive wasn't corrupted or truncated.
Archival & Backup Integrity
Record a hash when you archive a file so you can prove years later it hasn't changed.
QA & Build Verification
Confirm a build artifact matches the hash your CI pipeline produced before shipping it.
Why Use This File Checksum Verifier?
- Fully Client-Side: The Web Crypto API hashes your file in the browser — no upload.
- Five Algorithms at Once: MD5, SHA-1, SHA-256, SHA-384, SHA-512 — computed together.
- Verification-First UX: A clear match/mismatch verdict, not just hex you have to eyeball.
- Smart Paste Handling: Understands full checksum-file lines, not just bare hashes.
- Automatic Algorithm Detection: No dropdown to guess — length tells the tool everything.
- One-Click Copy: Copy any computed hash instantly.
- Nothing Saved: No local storage, no cookies — closing the tab clears everything.
- 100% Free & Private: No account, no tracking, no server involved.
File Checksum / Hash Verifier – Complete Guide
A download that completes without an error message isn't the same thing as a download that arrived intact. Corrupted downloads, interrupted transfers, and - far more rarely - tampered files can all produce a file that opens fine but isn't actually the one the publisher built. A checksum comparison is the one reliable way to know for certain.
What Is a File Checksum, Really?
A checksum is the output of a hash function run over every byte of a file. The defining property of a good hash function is that changing even a single byte of the input - one flipped bit from a bad download - produces a completely different, unpredictable output. So if the checksum you compute locally matches the one the publisher listed, you can be confident your copy is byte-for-byte identical to theirs.
How This Verifier Actually Works
When you drop a file, it's read into memory as raw bytes using the File API. Four of the five hashes - SHA-1, SHA-256, SHA-384, and SHA-512 - are computed with a single call each to crypto.subtle.digest(), the Web Crypto API's native, hardware-accelerated hashing function. MD5 isn't part of that API, so it's computed with a compact JavaScript implementation of the standard RFC 1321 algorithm instead. Whatever you paste into the expected-checksum box is trimmed of whitespace and, if it looks like a full checksum-file line, has the trailing filename stripped away automatically - what remains is measured by character length (32/40/64/96/128 hex characters map uniquely to MD5/SHA-1/SHA-256/SHA-384/SHA-512) to detect the algorithm, and that one computed hash is compared, case-insensitively, against your input to produce the verdict.
Checksum Verification vs Digital Signatures vs Just Trusting the Source
| Aspect | Checksum Verification (this tool) | Digital Signature | Trusting the Source Alone |
|---|---|---|---|
| Confirms | File matches a specific known-good copy | File came from a specific key holder | Nothing verifiable |
| Protects against | Corruption, incomplete downloads | Impersonation, unsigned tampering | Neither |
| Requires | The publisher's listed checksum | A trusted public key and signature file | Nothing - and offers nothing |
Common Hash Algorithms and Their Output Lengths
| Algorithm | Output Length | Typical Use Today |
|---|---|---|
| MD5 | 32 hex characters | Legacy download checks - fast but not attack-resistant |
| SHA-1 | 40 hex characters | Git commit hashes, some legacy checksums |
| SHA-256 | 64 hex characters | Modern default for ISO images and installers |
| SHA-384 | 96 hex characters | Occasionally used for TLS and enterprise software |
| SHA-512 | 128 hex characters | High-assurance releases and some Linux distributions |
Security and Privacy Considerations
- No Data Upload: Your file's contents never leave your device.
- No Server Processing: Every hash is computed entirely as client-side JavaScript.
- No Storage: Nothing about your file or result is saved once you close or refresh the tab.
- Checksum ≠ Authenticity: A matching checksum confirms the file is byte-identical to what the checksum was made for - it doesn't independently prove who made either one, unlike a digital signature.
Browser Compatibility and Technical Requirements
This File Checksum Verifier works in modern browsers that support:
- Web Crypto API (
crypto.subtle.digest): For SHA-1/256/384/512 hashing. - File API: To read a dropped or selected file's contents locally.
- Drag and Drop API: For the drag-and-drop upload zone.
Supported Browsers:
- ✅ Chrome/Edge 60+
- ✅ Firefox 57+
- ✅ Safari 11+
- ✅ Mobile Chrome (Android), Mobile Safari (iOS) — tap to browse instead of drag-and-drop
Troubleshooting Common Issues
Explanation: A trailing newline, extra space, or an accidentally copied second line can all change what was pasted. Solution: Re-copy just the hash itself from the publisher's page, or paste the full line - the tool strips a trailing filename automatically either way.
Explanation: What you pasted doesn't match any of the five supported hex lengths (32/40/64/96/128 characters) - it may include non-hex characters or be truncated. Solution: Double-check you copied the entire hash with nothing missing or extra.
Explanation: Reading a multi-gigabyte file into memory and hashing it is genuinely CPU and memory-intensive work happening on the main thread. Solution: Give it a moment to finish - avoid navigating away mid-hash, and prefer SHA-256 over MD5 for the fastest result on very large files.
Explanation: This tool verifies one file at a time by design, to keep the interface simple and clear. Solution: For batch verification, use your operating system's built-in checksum command (such as certutil, shasum, or sha256sum) against a full checksums file, and use this tool for spot-checks or when you're on a machine without command-line access.
Frequently Asked Technical Questions
Question 1: Which hashes actually use native browser crypto?
Answer: SHA-1, SHA-256, SHA-384, and SHA-512 are all computed with crypto.subtle.digest(), the Web Crypto API's native implementation. MD5 is not part of that API and is computed in plain JavaScript instead.
Question 2: How is the expected checksum's algorithm detected?
Answer: After trimming whitespace and stripping any trailing filename, the remaining hex string's length is measured - 32, 40, 64, 96, and 128 characters map uniquely to MD5, SHA-1, SHA-256, SHA-384, and SHA-512 respectively, so detection is exact, not a guess.
Question 3: How does the tool strip a filename from a checksum-file line?
Answer: Published checksum files commonly look like <hash>␣␣<filename> or <hash> *<filename>. The tool splits on the first run of whitespace and keeps only the first token, which is the hash itself.
Question 4: Is the comparison case-sensitive?
Answer: No. Hex hashes are conventionally written in lowercase, but some tools and publishers output uppercase - the comparison normalizes both sides to lowercase before checking for a match.
Question 5: Does this tool need an account, server, or API key?
Answer: No. The Web Crypto API and the File API are both built into modern browsers - you never need an account, backend, or API key to use this tool.
Glossary of Terms
- Checksum
- A fixed-length value computed from a file's contents, used to detect whether the file has been altered, corrupted, or incompletely downloaded.
- Hash Function
- An algorithm (such as MD5 or SHA-256) that converts data of any size into a fixed-length output, where even a one-bit change in the input produces a completely different output.
- SHA-256
- A member of the SHA-2 family of hash functions that produces a 256-bit (64 hex character) output, widely used for verifying software and ISO image downloads.
- MD5
- An older, fast hash function producing a 128-bit (32 hex character) output, still common for basic download-integrity checks but not considered secure against deliberate tampering.
- Hash Collision
- A case where two different pieces of data produce the same hash output - rare by chance but a known weakness of older algorithms like MD5 and SHA-1 when deliberately engineered.
Frequently Asked Questions
Yes, completely free with no signup and no limit on file checks.
No. The file is read and hashed entirely in your browser using the Web Crypto API and JavaScript. It never leaves your device or touches a network request.
A checksum confirms a downloaded file - such as an ISO image or software installer - is byte-for-byte identical to what the publisher intended, catching corrupted downloads, incomplete transfers, or tampering.
Each hash algorithm produces a fixed, unique output length: 32 hex characters for MD5, 40 for SHA-1, 64 for SHA-256, 96 for SHA-384, and 128 for SHA-512 - so the algorithm is detected automatically and unambiguously from the length of what you paste.
Yes. Lines like "a1b2c3... filename.iso" are common in published checksum files - the tool automatically extracts just the hash portion before comparing.
For confirming a download wasn't corrupted, yes - any mismatch, from any algorithm, reliably indicates a different file. MD5 and SHA-1 are no longer considered safe against a determined attacker deliberately crafting a matching file, so prefer SHA-256 or higher when a publisher offers it.
SHA-1 through SHA-512 use the browser's native, hardware-accelerated Web Crypto implementation, while MD5 isn't part of that API and runs as plain JavaScript, which is noticeably slower on very large files.
Yes, though the whole file is read into memory to compute the hash, so extremely large files (many gigabytes) on a low-memory device may take longer or strain available RAM.
Final Thoughts
A checksum takes a few seconds to check and eliminates an entire category of "why won't this install" or "is this actually safe" doubt. Whether you're verifying a Linux ISO, a signed installer, or a file you're archiving for the long term, dropping it in here gives you a definitive, byte-level answer - without ever sending the file anywhere.
Drop your file above and verify its checksum now!