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File Base64

Processed in this browser

File limit: 32 MB

This tool never uploads your input.

Drop a file

Drop a file here or choose one.

Sample workflow: drop any file to encode, or paste Base64 and download the bytes.

An API that wants a binary as a string. Anyone with the string can decode it. Do not Base64 a 25 MB PDF and expect Gmail to take the result.

A webhook example that says file_b64. This page maps bytes ↔ ASCII. It is not a vault.

Text-only: Base64. <img src="data:…">: image to Base64. Confidentiality: AES. Integrity of a download: file SHA-256.

Why attachments blow up

Base64 is roughly 33% larger than the raw bytes. Pasting a 20 MB PDF into a JSON field can miss Gmail’s 25 MB personal cap even when the original file would have attached. Use multipart when the API allows it. This is not a vault — anyone with the string can reverse it.

How to use it

  1. Drop a file this tab can hold (~32 MB).
  2. Encode or decode. Copy or download the bytes.
  3. If you planned to email the Base64, subtract the 33% tax first.

Honest limits

Not encryption. Not a streaming 4 GB encoder. Wrong alphabet (+/ vs -_) will fail a decode — match the API.

FAQ

Is Base64 encryption?

No. It is an alphabet. Use AES if you needed a key.

Why is the output larger?

Base64 expands about 33%. Gmail’s 25 MB cap is on the message, not your original file.

Text vs image vs file?

Text Base64 is the Base64 page. data:image/… is image to Base64. This page is arbitrary bytes.

JWT?

JWT is three Base64URL segments with structure. Use the JWT decoder.

Is the file uploaded?

No. About 32 MB typical.

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