Checksum Calculator
CRC-32, CRC-16 and Adler-32 for any text or file, side by side.
- Free
- No signup
- Nothing uploaded
- No watermark
cbf43926
The one in ZIP, PNG and gzip. 32 bits, polynomial 0xEDB88320.
bb3d
The plain CRC-16, polynomial 0xA001. Used by Modbus and older ZIP.
29b1
Starts at 0xFFFF with polynomial 0x1021. Different answer from CRC-16/ARC for the same bytes — check which one you need.
091e01de
Two rolling sums rather than a polynomial. Fast, and weak on short inputs.
How to Use the Checksum Calculator Online
CRC-32, CRC-16 and Adler-32 side by side for any text or file. All three detect accidental corruption and none of them detect tampering — they are not cryptographic, so a modified file can be adjusted to match. Use SHA-256 when the question is deliberate alteration.
No software to install Free Works on any device
Step-by-Step Guide to Using the Checksum Calculator
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1. Type or paste your text, or open a file to hash instead
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2. The hash appears straight away and updates as you type
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3. Paste a hash you were given into the compare box to check they match
What is the Checksum Calculator?
CRC-32, CRC-16 and Adler-32 side by side for any text or file. All three detect accidental corruption and none of them detect tampering — they are not cryptographic, so a modified file can be adjusted to match. Use SHA-256 when the question is deliberate alteration.
Why Use Security and Crypto Tools Locally?
Hashes, keys, tokens and passwords are exactly the things you should not paste into a stranger’s server. Here they are made and checked inside your browser, so secrets stay on the machine in front of you.
“A secret generated on your own device stays yours.”
- Strong random passwords
- Keys generated on your device
- Two-factor codes for testing
- Files checked against checksums
- Hashes in every common algorithm
- JWTs decoded and checked
- Security headers written for you
- No secrets sent anywhere
Popular Uses for Hash and Key Generators
Developers and careful users reach for these during everyday security work.
- New passwords Generate a long random password or passphrase for a new account.
- Verifying downloads Hash a file with SHA-256 and compare it with the value the publisher lists.
- Debugging logins Decode a JWT to see its claims and check the signature with your secret.
- SSH and API keys Create an RSA or Ed25519 key pair or an API key for a new service.
- Website headers Write a Content Security Policy and other security headers for a web server.
- Testing two-factor login Generate TOTP codes and secrets to test an authenticator setup during development.
- Script integrity Make an SRI hash so a browser can tell if a CDN script was changed.
- Password strength Measure how many guesses a password would take, using its entropy.
What You Can Do with the Checksum Calculator
Computed with the browser’s own WebCrypto implementation
Hashes the raw bytes, so a value can be checked against a publisher’s stated checksum
Works on a whole file rather than a pasted excerpt of it
Why Use ToolXkit for Checksum Calculator?
Your files stay with you
Everything runs inside your browser. Nothing you open or type is uploaded to a server.
Free, with no catch
No signup, no watermark and no daily limit on how often you use it.
Fast
Results appear in seconds, because nothing has to travel over the internet and back.
Works on any device
Use it on a computer, tablet or phone, in Chrome, Edge, Firefox or Safari.
Nothing to install
No app, no extension and no desktop program. Open the page and start.
Made for real people
Plain words and clear buttons, built by one developer who wanted tools like this to exist.
Crypto Tools for Different Users
Web developers
Create security headers, SRI hashes and JWTs while building and testing apps.
System administrators
Generate SSH keys, check fingerprints and verify file checksums on the go.
Security testers
Decode tokens, inspect PEM files and test HMAC signatures without extra tooling.
Computer science students
See how hashing, encryption and key pairs behave by trying them yourself.
Everyday users
Make strong passwords and passphrases that are never sent over the internet.
IT teams
Create API keys and OAuth values for new integrations in a safe place.
Best Times to Generate a Key or Hash
Local crypto tools make sense when you are:
- Setting up a new server
- Creating a strong password
- Checking a downloaded installer
- Debugging a sign-in problem
- Adding security headers to a site
- Testing an authenticator app
- Learning how encryption works
- Rotating an old API key
Frequently Asked Questions
Answers to common questions about this tool.
What is the difference between CRC-32, CRC-16 and Adler-32?
They are error-detection checksums of different widths and speeds. CRC-32 is used in ZIP archives and PNG files and is the general default; CRC-16 is common in embedded and serial protocols; Adler-32 is faster than CRC-32 and used by zlib, at the cost of weaker detection on very short inputs. All three are computed side by side so you can match whichever a specification asks for.
Can I use a checksum to verify a download is genuine?
For accidental corruption, yes — that is what these are designed for. For tampering, no. CRC and Adler are not cryptographic: someone altering a file can trivially adjust it to produce the same checksum. Use SHA-256 when the question is whether a file was deliberately modified.
Do I get the same value as my ZIP program?
For CRC-32, yes — it is the same standard polynomial ZIP uses, so a file checksum computed here matches what the archive reports. That makes it a practical way to check whether a file changed without unpacking anything.
Are the keys and passwords made here truly random?
They come from the browser’s built-in secure random number generator, the same source used for encrypted connections. That is suitable for passwords, keys and tokens.
Does Checksum Calculator send my secrets to a server?
No. Everything is worked out locally, and what you type or generate is neither uploaded nor logged. For real production keys, it is still wise to generate them on the machine where they will be used.
Is MD5 or SHA-1 safe to use?
Not for passwords or signatures, since both can be attacked. They are still fine for spotting accidental changes in a file. For security work, choose SHA-256 or stronger.
Is Checksum Calculator free for commercial projects?
Yes. Use it for personal, work or client projects at no cost and without an account. What you generate belongs to you, and the site keeps no copy.
Can a hash be reversed to get the original text?
No. A hash is one-way. Short or common passwords can still be guessed by trying many candidates, which is why a long, random password matters more than the hash you pick.
Further reading
- Hash Functions (NIST) NIST’s page on approved hash functions such as SHA-2 and SHA-3.
- RFC 7519: JSON Web Token (IETF) The standard that defines JSON Web Tokens and the claims inside them.
- RFC 6238: TOTP (IETF) The standard behind the six-digit codes shown in authenticator apps.
More Security & Crypto Tools
Other free tools for the same kind of job.
- Adler-32 Calculator Work out the Adler-32 checksum used inside zlib. Open tool
- AES Encrypt & Decrypt Encrypt or decrypt text with a password. Open tool
- AES Key Generator Generate a random AES-128 or AES-256 key. Open tool
- API Key Generator Generate API keys with a readable prefix and real entropy behind them. Open tool
- Bulk Password Generator Generate hundreds of strong passwords at once, with no modulo bias. Open tool
- CORS Header Generator Build CORS headers, with the wildcard-plus-credentials trap caught. Open tool
- CRC16 Calculator Work out CRC-16, both the ARC and CCITT variants. Open tool
- CRC32 Calculator Work out the CRC-32 checksum used by ZIP, PNG and gzip. Open tool
- CSP Generator Build a Content-Security-Policy, with the weak settings called out. Open tool