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Text Hash Calculator

Computes the MD5 (RFC 1321), SHA-1 (RFC 3174), SHA-256 (FIPS 180-4) and CRC-32 (IEEE 802.3 polynomial) digests of a text encoded as UTF-8, plus its byte length; all algorithms are implemented in plain JavaScript.

When to use

You need a checksum or digest of a short text to compare with a published value, generate a cache key or verify a test vector.

Do not use when: You need to hash a file or binary data, a keyed MAC (HMAC), a password hash (use bcrypt/scrypt/Argon2), or a hash of more than 200,000 characters.

Formula

digest = H(UTF-8(text)) for H ∈ {MD5, SHA-1, SHA-256}; CRC-32 = reflected CRC with polynomial 0x04C11DB7 (0xEDB88320 reversed), initial value 0xFFFFFFFF, final XOR 0xFFFFFFFF

Reference implementations of RFC 1321, RFC 3174 and FIPS 180-4 on 32-bit words; results match sha256sum / md5sum of the same bytes without a newline. The empty string cannot be submitted (its digests are d41d8cd9…, da39a3ee…, e3b0c442…).

Inputs

Parameter	Type	Unit	Required	Description
`text`	string		yes	The text to hash; it is encoded as UTF-8 without a trailing newline (echo -n).

Outputs

Output	Type	Unit	Description
`md5`	string		128-bit MD5 digest, 32 lower-case hex characters (broken for collision resistance; checksums only).
`sha1`	string		160-bit SHA-1 digest, 40 hex characters (deprecated for signatures).
`sha256`	string		256-bit SHA-256 digest, 64 hex characters.
`crc32`	string		CRC-32 (polynomial 0xEDB88320, as in zlib, PNG and Ethernet), 8 hex characters.
`crc32_decimal`	integer		The same CRC-32 as an unsigned integer.
`byte_length`	integer	bytes	Length of the UTF-8 encoding that was hashed.
`character_count`	integer		Number of Unicode code points in the text.

Example

hello: {"text":"hello"} → {"md5":"5d41402abc4b2a76b9719d911017c592","sha1":"aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d","sha256":"2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824","crc32":"3610a686","byte_length":5}

The quick brown fox jumps over the lazy dog: {"text":"The quick brown fox jumps over the lazy dog"} → {"md5":"9e107d9d372bb6826bd81d3542a419d6","sha1":"2fd4e1c67a2d28fced849ee1bb76e7391b93eb12","sha256":"d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592","crc32":"414fa339","byte_length":43}

GET https://tttkmbb.com/api/v1/calculate/text-hash?text=hello

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/text-hash (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/text-hash · Markdown: https://tttkmbb.com/developer/text-hash.md · JSON definition: https://tttkmbb.com/developer/text-hash.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="text-hash"
OpenAPI operationId: calculate_text_hash
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

RFC 1321 – The MD5 Message-Digest Algorithm (standard)
RFC 3174 – US Secure Hash Algorithm 1 (SHA1) (standard)
NIST FIPS 180-4 – Secure Hash Standard (SHS) (standard)

FAQ

Why does my result differ from echo text | md5sum?

echo appends a newline, so the shell hashes one extra byte. Use echo -n or printf '%s' to hash the bare text.

Which hash should I use?

SHA-256 for integrity and signatures. MD5 and SHA-1 are cryptographically broken (collisions can be manufactured) and CRC-32 detects accidental corruption only.

How are non-ASCII characters handled?

The text is encoded as UTF-8 first, so 'é' contributes 2 bytes and an emoji 4; byte_length reports the encoded size.

Related calculators

Base64 Size Calculator — Size of the same data once Base64-encoded.
Password Entropy Calculator — Strength of a secret rather than its digest.
Number Base Converter — Read hex digests as decimal or binary.