What is Base64 File Encoder?

A file-to-base64 encoder that converts any file into a base64-encoded text string. Useful for embedding files in JSON, HTML, CSS, or transferring binary data through text-only channels.

Pick or drag a file up to 50 MB and the encoder reads it locally, converts the bytes to Base64, and shows the result with the file size, detected MIME type, and a complete data URI. Switch the output format to wrap the bytes as JSON, XML, or a ready-to-paste HTML download link for any file type, and check the inline JavaScript, Python, and Shell snippets for the matching decode call. Switch to Decode mode to paste a Base64 string back and download the original file, and use the line-wrapping and strip-padding controls to fit MIME, PEM, or JWT output exactly.

How to use

1. Upload or drag-and-drop any file (images, documents, audio, etc.) into the encoder.
2. View the generated base64 string along with the file size, MIME type, and data URI format.
3. Copy the base64 string or data URI to your clipboard, or download it as a text file.

When to use

• Embedding a small icon or font directly inside a CSS file with a data URI to remove a network request.
• Pasting binary content into a JSON payload for an API that does not accept multipart uploads.
• Sharing a sample test file as plain text in a bug ticket where attachments are not allowed.

Result

A developer needs to embed a small icon directly in a CSS stylesheet. They upload a 2KB favicon.png and copy the generated data URI to use as a background-image value.

FAQ

Why is the encoded text roughly one-third larger than my original file?

Base64 represents every 3 bytes of input as 4 ASCII characters, so the output grows by about 33%. A 2 KB image becomes around 2.7 KB of text. If you embed many files this way, the size cost is real — keep an eye on it for large CSS bundles.

What is the difference between the Base64 output and the data URI?

The Base64 string is just the encoded bytes. The data URI wraps it as data:<mime>;base64,<text> so a browser or email client can render the file inline. Use the data URI in HTML or CSS; use the raw string when the consumer adds its own prefix.

Can I encode a 200 MB video here?

The encoder caps uploads at 50 MB to stay responsive — Base64 of a 200 MB file is roughly 270 MB of text and most editors slow to a crawl on strings that large. For big media, use a CDN URL or a server-side encoder instead.

Does the MIME type really matter or can I always use application/octet-stream?

The MIME type is what lets the receiver render or save the bytes correctly. A PNG embedded in HTML must declare image/png so the browser draws it inline; misdeclaring it falls back to a download prompt or a broken image icon.

Is the file uploaded somewhere when I encode it?

No. The conversion happens locally on your device with the FileReader API, so the bytes never leave your machine. You can verify by encoding offline — pull the network plug, drop a file in and it still works.

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