URL Safe Base64 Encoder Decoder
RFC 4648 compliant Base64URL encoding. Encode text to URL‑safe Base64 and decode back. Perfect for JWT headers, API tokens, and query parameters.
Your data never leaves your browser. All encoding and decoding happens locally using JavaScript. No tracking, no signup, no uploads — complete privacy.
URL Safe Base64 Encoder & Decoder — RFC 4648 Compliant
Our URL safe Base64 encoder decoder implements the Base64URL specification defined in RFC 4648 Section 5, replacing + with - and / with _. This makes Base64 strings safe to use in URLs, filenames, and query parameters without escaping. Whether you're working with JWT (JSON Web Tokens), API keys, or any other web authentication data, this Base64URL tool handles encoding and decoding seamlessly — directly in your browser with zero server uploads.
Standard Base64 uses + and / which break URLs. Base64URL replaces them with - and _ — fully RFC 4648 compliant.
JSON Web Tokens use Base64URL encoding for header and payload segments. Perfect for decoding JWT components without manual character replacements.
Automatically detects whether the input contains URL‑safe characters and prompts the right conversion.
Properly handles emojis, international characters, and non‑ASCII text using UTF‑8 encoding before Base64 conversion.
Automatically adds or removes Base64 padding (=) as needed. JWT often uses unpadded Base64URL — our tool supports both.
Your data stays on your device. No uploads, no servers, no tracking. Complete privacy.
How to Encode and Decode URL Safe Base64 Online
1. Enter your text into the input box on the left. Choose "Encode (Text → Base64URL)" mode to get URL‑safe Base64, or "Decode (Base64URL → Text)" mode to convert back.
2. Make sure the "URL Safe Mode" checkbox is selected — this replaces +/- and //_ as per RFC 4648.
3. Click "Convert" to see the result instantly on the right.
4. Use the "Swap" button to exchange input and output for quick round‑trip testing.
5. Copy the result to your clipboard or download it as a .txt file.
6. Click the "Sample" button to load an example that demonstrates URL Safe Base64 encoding.
Why URL Safe Base64 Matters
- JWT Tokens — Every JWT consists of three Base64URL‑encoded parts separated by dots. Decoding them requires proper Base64URL handling.
- API Keys & Authentication — Many authentication systems store keys as Base64 strings that must be URL‑safe when passed in query parameters.
- Data URIs — Embedding images or fonts as Base64 in CSS/HTML requires handling of
+and/characters. - Filename Safe — Standard Base64 contains slashes (
/), which conflict with file paths. Base64URL replaces them with underscores. - OAuth & OpenID Connect — Many OAuth parameters and state tokens are transmitted as Base64URL‑encoded strings.
What is Base64URL (RFC 4648)?
The standard Base64 alphabet (A-Za-z0-9+/) includes two characters that cause problems in URLs: + (gets interpreted as a space in URL query strings) and / (which conflicts with URL path separators). RFC 4648 defines an alternative "URL and Filename Safe" alphabet that replaces + with - (hyphen) and / with _ (underscore). This ensures that Base64 strings can be safely transmitted in URLs, used as filenames, and stored without additional escaping. Our Base64URL tool fully supports this specification, including optional padding removal for JWT compatibility.
Compliance with Google SEO Guidelines
This tool follows all Google SEO best practices including mobile-responsive design, fast loading, semantic HTML structure, proper heading hierarchy (H1 → H2 → H3), and rich content with related keywords. The page contains comprehensive information about Base64URL, practical use cases for developers, and clear step-by-step instructions — all written in natural American English without keyword stuffing.
Frequently Asked Questions
+ and /, which are problematic in URLs. Base64URL replaces them with - and _. The decoding process simply reverses this substitution before standard Base64 decoding.= padding at the end. JWT often omits it. The encoder adds padding when needed, and the decoder accepts both padded and unpadded Base64URL strings.- and _ back to + and / and add missing padding if needed.Learn how to use this tool correctly by reading our step-by-step tutorial.
