About CRC32 Checksum Calculator
This CRC32 calculator computes the standard CRC-32 checksum of your text or file, the one used by ZIP, gzip, PNG and Ethernet. It is a 32-bit value, written as 8 hexadecimal characters. It is free, needs no sign-up and runs in your browser, so nothing you enter is uploaded.
CRC32 is a cyclic redundancy check, not a cryptographic hash. It is designed to notice accidental damage, such as a flipped bit on a disk or a noisy link, and it does that very quickly. It does not resist deliberate tampering: it is simple to craft a different input with the same CRC32. Never use it for signatures or passwords.
Typical uses are comparing a file with the CRC column shown by an archive tool, checking a ROM or a split archive, and debugging file formats that store a CRC. The version here is CRC-32 with the reflected polynomial 0xEDB88320, initial value 0xFFFFFFFF and a final XOR, which is the variant usually just called CRC32. Other CRC32 variants, such as CRC-32C used by iSCSI and some storage systems, give different values.
The result is shown as 8 hex digits with leading zeros kept, so the CRC32 of an empty input is 00000000. HMAC is not offered for CRC32, because a keyed CRC would give no security.
How to use CRC32 Checksum Calculator
- Choose an algorithm from the row of buttons: MD5, SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA3-256, SHA3-512 or CRC32. SHA-256 is a good default.
- Choose Text and type or paste your input, or choose File and pick a file from your device. The hash updates as you type.
- Read the digest in the result box. Tick Uppercase for capital hex letters, or Base64 output to show the digest in Base64 instead of hex.
- For a keyed hash, tick HMAC with secret key and enter the key. The result is then labelled HMAC-SHA-256 (or whichever algorithm you chose).
- To verify a download or a value from documentation, paste the expected hash into Compare with a known hash. The tool says Match or No match.
- Use Copy to put the digest on your clipboard.
Features
- Nine algorithms: MD5, SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA3-256, SHA3-512 and CRC32.
- Hashes text as UTF-8, so accented letters, other scripts and emoji hash the same way as on a server or in a command-line tool.
- Hashes a file you choose from your device. The file is read in your browser and never uploaded.
- HMAC with a secret key for every algorithm except CRC32, following RFC 2104.
- Hex output in lowercase or uppercase, or Base64 output.
- Compare with a known hash. Case, spaces and a leading 0x are ignored, and the expected value can be hex or Base64.
- SHA-1, SHA-256, SHA-384 and SHA-512 use the Web Crypto API in your browser, which is fast and well tested.
- A warning appears when you pick MD5, SHA-1 or CRC32, because they are not safe for security purposes.
- One-click copy of the result.
Worked examples
CRC32 of "123456789" gives cbf43926
The standard check value for CRC-32.
CRC32 of "abc" gives 352441c2
CRC32 of "Hello, World!" gives ec4ac3d0
CRC32 of an empty input gives 00000000
Privacy: how it works
- The text, the file and the HMAC key stay in your browser tab. Nothing is sent to Ulkaa or to any other server, which you can confirm in the Network tab of your browser developer tools.
- Because the work happens on your own device, large files are limited by your browser memory rather than by an upload limit.
Tips
- To verify a download, choose File, pick the downloaded file, and paste the publisher hash into the compare box. A match means the bytes are identical to what the publisher hashed.
- Hash the same text twice with a trailing space added once. Seeing two unrelated digests is the quickest way to understand the avalanche effect.
- A hash you found on the same page as the download only protects against corruption. It cannot protect you if the page itself was altered.
- HMAC takes the key as plain text. If your key is hex or Base64, decode it first, or the result will not match another system.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Your text and files are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Your text and files are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
Is CRC32 secure?
No. It catches accidental errors only. Anyone can build a different file with the same CRC32, so it must not be used to detect tampering.
Why does my CRC32 not match another tool?
Check the variant. This tool uses standard CRC-32 (IEEE 802.3, as in ZIP and PNG). CRC-32C, CRC-32/BZIP2 and others use different settings and give different results. Also check for a trailing newline in the input.
How do I check a CRC32 for a file?
Choose File, pick the file, and read the 8-character value. Paste the expected CRC into the compare box. Case and a leading 0x are ignored.
More Hash Generator pages
- Hash GeneratorHash text or a file with MD5, SHA-1, SHA-2, SHA-3 or CRC32, add an HMAC key, and check the result against a known hash.
- MD5 Hash GeneratorGet the 128-bit MD5 hash of text or a file as 32 hexadecimal characters.
- SHA-1 Hash GeneratorGet the 160-bit SHA-1 hash of text or a file as 40 hexadecimal characters.
- SHA-224 Hash GeneratorGet the 224-bit SHA-224 hash of text or a file as 56 hexadecimal characters.
- SHA-256 Hash GeneratorGet the 256-bit SHA-256 hash of text or a file as 64 hexadecimal characters.
- SHA-384 Hash GeneratorGet the 384-bit SHA-384 hash of text or a file as 96 hexadecimal characters.
- SHA-512 Hash GeneratorGet the 512-bit SHA-512 hash of text or a file as 128 hexadecimal characters.
- SHA3-256 Hash GeneratorGet the 256-bit SHA3-256 hash of text or a file as 64 hexadecimal characters.
- SHA3-512 Hash GeneratorGet the 512-bit SHA3-512 hash of text or a file as 128 hexadecimal characters.
- HMAC-SHA256 GeneratorSign a message with a secret key using HMAC-SHA256 and read the result as hex or Base64.
- File Checksum CalculatorHash a file on your device and compare it with the checksum the publisher gave you.