Base64URL Encoder transforms standard text, JSON payloads, and binary data into a URL-safe Base64 string. Standard Base64 uses characters (`+`, `/`, `=`) that break URLs and query parameters. Base64URL explicitly replaces these with URL-safe variants (`-`, `_`), allowing data to be seamlessly transmitted in HTTP GET requests, JWTs (JSON Web Tokens), and OAuth redirect states.
Standard Base64 encoding translates binary data into 64 printable ASCII characters. However, its use of `+` and `/` conflicts with URI syntax (like directory slashes or query concatenation). Base64URL (defined in RFC 4648) purposefully swaps `+` for `-` (minus) and `/` for `_` (underscore). It also typically omits the trailing `=` padding characters, resulting in a perfectly clean, URL-ready string.
Standard Base64 uses the character set [A-Z, a-z, 0-9, +, /] and pads with [=]. Base64URL replaces the plus sign (+) with a minus (-), replaces the slash (/) with an underscore (_), and entirely strips the equals (=) padding.
The equals sign (=) is normally used to separate keys and values in URL query strings (e.g., ?token=value). Including it inside the value itself can confuse some backend URL parsers, so the standard dictates removing it.
Yes. Every JSON Web Token consists of three parts (Header, Payload, Signature) that are independently encoded using Base64URL and joined together with periods (.).
No! Base64URL is strictly an encoding standard for data transport, not encryption. Anyone who intercepts the string can instantly decode it back to plain text.
Absolutely not. The encoding algorithm runs via native JavaScript (`btoa` with regex replacements) entirely on your local machine.
Yes, it is 100% free with no usage limits.
Tool workspace
Free Base64URL encoder online — instantly transform strings and JSON payloads into URL-safe Base64 encoding. Perfect for JWT tokens and web APIs. No login.
Output
Input
{"alg":"HS256","typ":"JWT"}Output
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9