Base64 Detector

Paste any string and instantly detect which Base64 variant it uses. Get detailed analysis with confidence levels and character breakdown.

Last Updated: September 2026
100% Client-Side — Your data never leaves your device

Paste a string to detect which Base64 variant it uses

Why this tool is safe

Your data never leaves your device — everything runs in your browser.

No server uploads. Other tools send your files to their servers. Ours don't.
Zero tracking of content. We never see, store, or log anything you convert.
Works offline. Once loaded, the tool works without an internet connection.
No account required. Instantly use all tools completely free without signing up.

Frequently Asked Questions

Search below or browse through our most commonly asked questions.

While standard Base64 uses + and / for its 62nd and 63rd characters, URL-safe Base64 uses - and _ instead so the string can be safely passed in web addresses without URL encoding.
The detector uses pattern matching heuristics. If a string only contains alphanumeric characters, it may be impossible to tell if it's standard or URL-safe, so the tool will output a 'Medium' or 'Low' confidence score.

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