Base64 Decode
Decode a Base64-encoded string back to plain text. Handles UTF-8, URL-safe variants, and strings with or without padding.
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What is Base64 decoding?
Base64 decoding is the inverse operation of Base64 encoding: it converts a Base64 ASCII string back into the original sequence of bytes. Once you have the bytes, you can interpret them as text (using UTF-8 or another encoding) or as binary data like an image or file.
How to use this Base64 decoder
- Paste your Base64 string into the left panel, or click Upload to load a file.
- Leave Auto-detect on to handle both standard and URL-safe variants automatically.
- Click Decode →. The original text appears instantly on the right.
- Click Copy or Download to export the decoded text.
When to decode Base64
- Reading JWTs — the header and payload of a JSON Web Token are URL-safe Base64. Decode them to inspect claims.
- Debugging HTTP —
Authorization: Basicheaders contain Base64user:pass. - Reverse-engineering data URIs —
data:image/png;base64,…can be decoded back to the original bytes. - Inspecting MIME emails — message bodies and attachments are often Base64-encoded.
- Decoding API responses — many APIs return binary blobs as Base64 inside JSON.
Standard vs. URL-safe Base64
Two common variants exist:
- Standard — uses
+and/with=padding. Defined in RFC 4648 §4. - URL-safe — uses
-and_with padding often omitted. Defined in RFC 4648 §5, used in JWT, OAuth, and URL tokens.
This tool auto-detects which variant you pasted and handles both transparently.
Privacy
All decoding happens in your browser. No input ever leaves your device — not even for analytics. The tool works fully offline once the page is loaded.