Base64 Decoder – Decode Base64 Online (Free Tool)
Free online Base64 Decoder tool to decode Base64 encoded text back to its original format. Convert Base64 strings to readable text, images, or binary data instantly. Handles URL-safe Base64 variants and standard encoding. All decoding happens locally in your browser ensuring complete privacy and security.
What is Base64 Decoder?
Base64 Decode converts a Base64-encoded string back to its original text or binary. Use it to inspect data inside JWTs, decode email headers, read MIME-encoded attachments, or recover text from a copy-pasted token. Decoding happens locally in your browser — sensitive payloads (auth tokens, API responses) are never transmitted to a server.
Why use this tool?
- No telemetry, no tracking pixels, no third-party scripts
- Open-and-go: bookmark the page once and never look for an alternative
- Instant results — no waiting on a server or upload progress bar
- Built for developer workflows: copy-friendly output, syntax-aware highlighting where useful
- Works with very large inputs (multi-megabyte JSON, long regex patterns, big tables)
How to use
- Paste your input into the base64 decoder area
- Configure the options if the defaults don't match your case
- Click the action button and inspect the result
- Copy the output to your clipboard or download as a file
Examples
Decode a JWT payload
Copy the middle segment of a JWT (between the two dots) and decode it to reveal the JSON claims — useful when debugging an auth bug.
Read a Data URL
Strip the "data:image/png;base64," prefix and decode the rest to inspect or save the raw bytes of an embedded image.
Reverse an HTTP Basic auth header
Decode the Base64 string after "Basic " to recover the username:password sent in an Authorization header (in your own dev env, of course).
Common use cases
- Inspecting JWT payloads while debugging authentication
- Recovering plain text from email "MIME-Word" encoded subjects
- Reading binary payloads pasted into a chat or log
- Verifying a Base64 string matches expected content during integration testing
- Reverse-engineering tokens embedded in URLs or HTML attributes
Troubleshooting
- Decoded output looks like gibberish.
- The input is probably binary (image, PDF, compressed data). Plain-text decode is meaningless — save to a file with the right extension instead.
- Error: "Invalid character in Base64 string".
- The string may use Base64URL (- and _ instead of + and /). Toggle the URL-safe option, or manually replace - with + and _ with /.
- Decoded text shows or weird characters for accents.
- The original was UTF-8 but is being read as Latin-1. Use a tool that decodes the bytes as UTF-8, or paste the result into a UTF-8-aware viewer.
Frequently Asked Questions
Base64 decoding converts Base64-encoded strings back to their original binary or text format. It reverses the encoding process to retrieve the original data.
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