No upload, 100% local, no account

Base64 Encoder / Decoder

Encode text or files to Base64 (including data URIs), or decode Base64 back to text. Nothing leaves your device.

How Base64 Encoder / Decoder works

Base64 encode and decode handles both text strings and binary files in one place. Paste or type text to get the Base64 representation, or drop any file, an image, a certificate, a PDF, to get its Base64 string ready to embed in data URIs, email attachments or API payloads. Decoding works in reverse for both text and files.

It reads files with the FileReader API and converts the raw bytes with the built-in btoa/atob routines of the browser. A URL-safe variant swaps + and / for - and _ so the output can sit in a URL or filename without percent-encoding.

Frequently asked questions

Are my files uploaded to a server?

No. Encoding and decoding run in your browser tab, files are read into memory on your own device with the FileReader API and converted using the browser's built-in Base64 routines (btoa/atob over the raw bytes), then the result is shown or offered as a local download. Nothing reaches Sunasty or any third party. Open your browser's DevTools, go to the Network tab and watch: no request carries your file.

What is the difference between standard Base64 and URL-safe Base64?

Standard Base64 uses + and / characters, which have special meanings in URLs. URL-safe Base64 replaces those with - and _ so the output can be embedded in a URL or a filename without percent-encoding. The tool lets you choose the variant you need.

Can I decode a Base64 string back to a file?

Yes. Paste a Base64-encoded string and the tool decodes it to bytes and offers a download. If the original was an image or PDF the browser will recognise it by its decoded magic bytes.

Does it work offline?

Yes, once the page has loaded. Because the processing happens on your device, you can disconnect from the network and the tool keeps working. This is the clearest proof that your data never leaves your machine.

Is it free? Do I need an account?

It is completely free and requires no sign-up. There are no watermarks, no daily limits and no tracking cookies needed to use the tool.