Base64 vs Base64URL

Base64URL is a URL-safe variant used in JWTs and query strings.

Standard Base64 uses + and /.
Base64URL replaces them with - and _.
Base64URL may omit = padding.

// Convert Base64URL -> Base64
const b64 = b64url.replace(/-/g, '+').replace(/_/g, '/');
const padded = b64.padEnd(Math.ceil(b64.length / 4) * 4, '=');

If decoding fails, first normalize URL-safe characters and restore padding.

Continue with related guides

Browse the full guides hub or open the Base64 encode/decode tool.

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