Free online developer tools

Browse 13 focused utilities for common development tasks. Each tool runs in your browser, requires no account, and does not upload the text or files you provide.

Format & convert

Pretty-print, validate, and move data between JSON, YAML, and CSV.

JSON formatter Pretty-print or minify JSON and get the exact line and column of any syntax error. JSON ↔ YAML Convert between JSON and YAML in either direction, preserving types and key order. CSV ↔ JSON Turn CSV into an array of objects and back, with delimiter and header control.

Encode & decode

Base64, percent-encoding, and JWT inspection — text and files.

Base64 Encode or decode Base64 and Base64URL for UTF-8 text or any file, with no size limit beyond your RAM. URL encode Percent-encode or decode a full URL, a query component, or a single path segment. JWT decoder Decode a JSON Web Token’s header and payload, expand standard claims, and flag alg:none and expired tokens.

Hash & HMAC

Checksums and keyed digests computed in your browser with SubtleCrypto.

Hash generator Compute MD5, SHA-1, SHA-256, and SHA-512 digests of text or a file, with hex and Base64 output. HMAC generator Compute a keyed HMAC over a message using SHA-1, SHA-256, SHA-384, or SHA-512.

Generate

Identifiers and tokens with predictable, spec-correct output.

UUID / ULID Generate cryptographically random UUID v4 values and lexicographically sortable ULIDs in bulk.

Time & scheduling

Unix timestamps across time zones and cron expressions in plain English.

Cron builder Build a cron expression from fields, read it back in plain English, and preview the next five run times. Timestamp converter Convert Unix seconds or milliseconds to a human date in any time zone, and back.

Text & patterns

Regular-expression testing and line/word-level diffing.

Regex tester Test a JavaScript regular expression against sample text and inspect every match and capture group. Text diff Compare two blocks of text and see additions and deletions highlighted at the word level.

Choose the right encoding or cryptographic tool

Use Base64 to turn bytes into portable text, the JWT decoder to inspect token headers and claims, a hash to fingerprint data, and HMAC when a shared secret must authenticate a message. Encoding is reversible; hashing and HMAC serve different integrity and authentication purposes.