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LocalThis runs in your browser. Nothing you paste is sent anywhere.

Base64 · Local tool

Base64 decode and encode

Decode base64 to text, or encode text to base64, without leaving the page.

Last updated

  1. 01 / Your device

    the file stays here

  2. 02 / Browser memory

    the work runs locally

  3. 03 / Back to you

    saved on this device

When you would use this

Situations, not settings.

A token or header you need to read
JWT payloads and basic auth headers are base64. Decoding them in the page keeps them out of anyone's logs.
A data URL you want to inspect
Handles UTF-8, emoji and the URL safe alphabet rather than falling over on them.
Encoding something for a config file
Goes both ways, and nothing you paste leaves the tab.

How it works / no cloud

A conversion engine, not an upload form.

The conversion happens in JavaScript on the page as you type. There is no request to make: base64 is a text transformation, and a server would only add a round trip and a copy of your data on someone else's disk.

  • Offline ready
  • Installable app
  • No file limit queue

Straight answers

No accordion. Nothing hidden.

Is it free?
Yes, with no watermark and no page limit.
Does it need an account?
No. There is no account system.
Is my file processed on my device?
Yes. The file is read by your browser and never uploaded. There is no server to send it to.
What formats are supported?
Text in either direction. Accepts line breaks, missing padding, the URL-safe alphabet, and a data: URL prefix. Output can be copied or downloaded as .txt.
What are the limits?
Bounded by what your browser will hold in a text box, which in practice is several megabytes. Base64 that decodes to a file rather than text is offered as a download instead.
Does it work on mobile?
Yes, on any modern mobile browser. Large files are limited by the memory the phone gives the browser.
Does it work offline?
Yes, after you have used it once. Your browser keeps what the tool needs, so it then works with no network connection.
Why does my accented or non-English text come back wrong elsewhere?
Because most quick base64 tools, and the browser's own atob and btoa, work on latin1 rather than UTF-8. Anything outside the first 256 characters gets mangled, and emoji break outright. This tool encodes and decodes through UTF-8, so text goes in and comes back identical.
Can I paste a whole data: URL?
Yes. A prefix like data:image/png;base64, is stripped before decoding, so you can paste what you copied out of CSS or HTML without trimming it first.
What if it decodes to a file rather than text?
You get told, and offered the bytes as a download. Showing them as text would produce a screen of replacement characters that looks like a broken decode, so the tool checks whether the result is valid UTF-8 before claiming it is text.
Is base64 encryption?
No, and it is worth being clear about. Base64 is an encoding, not a cipher. Anyone can decode it in one step, exactly as you are doing here. It hides nothing.
What does a remainder of one mean in the error?
That a character went missing. Base64 turns every three bytes into four characters, so a valid string's length, with padding removed, is never one more than a multiple of four. The tool says how long yours is; check the start and end of what you copied.

Keep working locally

7 available · more coming