File to Base64
File to Base64 reads only the first selected file through FileReader and returns the portion after the data-URL comma: the raw Base64 payload without a data: prefix or MIME type. Base64 is reversible text encoding, not encryption or compression, and usually expands binary data by roughly one third before surrounding text overhead.
Runs locally — files stay on your deviceDoes the output include a data URL prefix?
No. Only the Base64 payload is returned.
Base64 represents binary bytes with text characters
Groups of three input bytes become four ASCII characters, with equals signs used as padding when needed. Anyone can decode the result.
How it works
FileReader.readAsDataURL loads the first file, then the page removes everything through the first comma and displays the remaining Base64 text.
Key concepts
Payload only
The output omits media type and data-URL syntax.
Byte identity
Correct decoding recreates the original bytes.
When to use it
- Embed a small binary payload in a format that requires Base64.
- Inspect or copy an encoded file value.
- Transport bytes through a text-only field.
When not to use it
- Do not use Base64 to protect secrets.
- Do not expect a smaller payload.
- Do not paste very large output into systems with text limits.
Worked examples
Small text
- Input
Bytes for Hello- Expected output
SGVsbG8=
Padding completes the final group.
Image embedding
- Input
logo.png- Expected output
Base64 only
Add an appropriate data:image/png;base64, prefix if required.
Two selections
- Input
a.bin and b.bin- Expected output
Encoding of a.bin only
The operation uses the first file.
Common mistakes
Calling it encrypted
Decoding requires no key. Correction: Use authenticated encryption for confidentiality.
Expecting a data URL
The prefix is stripped. Correction: Add the verified MIME prefix at the destination.
Selecting multiple files
Only the first is encoded. Correction: Process files individually.
Best practices
- Use it for small, deliberate payloads.
- Record the correct media type separately.
- Decode and compare a hash when exact round-trip integrity matters.
Related operations and differences
Add Prefix to Filenames
Choose Add Prefix to Filenames when you need to add a prefix to selected filenames.; use File to Base64 specifically for base64.
Add Suffix to Filenames
Choose Add Suffix to Filenames when you need to add a suffix before every extension.; use File to Base64 specifically for base64.
Compare Two Files
Choose Compare Two Files when you need to compare two files securely by SHA-256.; use File to Base64 specifically for base64.
File Checksum Comparator
Choose File Checksum Comparator when you need to compare a file digest with an expected checksum.; use File to Base64 specifically for base64.
File Hash Calculator
Choose File Hash Calculator when you need to calculate a local cryptographic file digest.; use File to Base64 specifically for base64.
File Size Calculator
Choose File Size Calculator when you need to inspect exact and human-readable file sizes.; use File to Base64 specifically for base64.
Limitations and privacy
- Only the first file is encoded.
- The entire file and expanded output occupy browser memory.
- No wrapping, download, data-URL prefix, encryption, or compression.
Processing happens in this browser. Selected file contents are not uploaded by this tool.
Downloads and copied results remain on this device; handle them according to their sensitivity.
Frequently asked questions
Can Base64 be decoded?
Yes, without a password.
Does it preserve bytes?
A correct decoder reconstructs them.
Why is output larger?
Base64 uses four characters for each three-byte group.
Are multiple files encoded?
No.