Base64 encoder / decoder
Encode text into Base64, or decode a Base64 string back, with accents and special characters handled correctly as UTF-8. It is the encoding behind HTTP headers, data-URI images and a good chunk of debugging. The string is processed on your device, so a secret encoded in Base64 never leaves your machine.
- 100% local
- Free · no account
- Instant result
This tool runs entirely in your browser — nothing is sent to a server.
Base64 encodes binary data into printable characters (A-Z, a-z, 0-9, +, /) — essential for data-URIs, HTTP Basic authentication headers, API keys or e-mail attachments. It is not encryption: anyone can decode a Base64 string.
This tool encodes and decodes while handling UTF-8 correctly: accents, symbols and emojis survive the round trip, where plain JavaScript btoa() fails on non-Latin characters.
How it works
Type the figures or drop the file you want to process — the tool checks them as you go.
Everything is computed directly in your browser. Nothing is sent to a server.
The result appears instantly, with the detailed breakdown ready to copy, download or keep.
Why use this tool
No account, no download, no limit: the result appears as soon as you enter your data.
Every rule, algorithm and check reflects what we use ourselves every day at Flexina.
The calculations follow the official standards, and the step-by-step detail lets you double-check the outcome.
What does running it locally bring you?
Files, figures and documents never leave your device: nothing is stored, nothing is sent.
Once the page is loaded, you can cut the network: the tool keeps working.
No upload, no account, no third-party server in between: results stay fast and fully private.
Frequently asked questions
Does Base64 protect my data?
No, it is encoding, not encryption: it decodes instantly, with no key. Never use it to “hide” a password or sensitive data.
Why is my decoded string unreadable?
Either it was not Base64, or the decoded content is binary (image, file) rather than text. Replacement characters (U+FFFD) indicate non-textual content or an encoding other than UTF-8.
What do the = signs at the end mean?
It is padding, to align the length to a multiple of 4. It is sometimes omitted (the Base64URL variant used in JWTs, with - and _ instead of + and /).