Base64 File Encoder & Decoder Online — Free
Runs 100% in your browser — your files never leave your device.
Embedding an image in CSS, pasting a file into a support ticket, or decoding a base64 blob someone sent you — this tool goes both ways. Drop a file to get its base64, or paste base64 (data URIs included) and download the reconstructed file. Everything happens locally, so even private files stay on your device.
How it works
- 1
Drop a file or paste base64
Either direction works: file in, base64 out — or the reverse.
- 2
Copy or name the output
Copy the encoded string, or give the decoded file a name.
- 3
Download
Decoded files download instantly, mime type detected from data URIs.
About this tool
Files as base64 text
The tool encodes any file into its complete base64 text — including data-URI form for embedding — and decodes base64 back into the original file bytes. Images in CSS and HTML data URIs, file payloads in JSON, and text-only transfer channels all run through this format.
The size arithmetic
Base64 grows data by about a third, so a 1 MB file becomes roughly 1.35 MB of text. Embedding files as data URIs trades that size for a zero-request asset — right for small images and fonts, wasteful for anything large.
Round-trip fidelity
Decoding produces the exact original bytes — verified by magic bytes on the decode path, so a decoded PNG is a real PNG, not a text approximation. Encode and decode run entirely in your browser; files never leave the device.
Frequently asked questions
What is a data URI?
A URI that carries the entire file inline — data:image/png;base64, followed by the base64. Browsers render it like a normal file reference; the tool can emit that form directly.
Why is my decoded file corrupt?
The base64 text was not a clean encoding of a file — trailing whitespace, wrapped lines, or a truncated string. Re-encode from the original source if you have it.
Is there a file size limit?
The browser is the limit — files of several megabytes encode instantly. Very large files produce very large text, which is the practical ceiling.