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Base64 encoder and decoder

Encode text or files to Base64 and decode Base64 or Base64URL locally, with strict validation, Data URL output, and binary download.

Work happens in the current browser. The route does not require an account or a server-side processing job.

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Interactive browser workspace

Base64 encoder and decoder

The live tool is loaded in this browser only. This route does not need camera, microphone, or screen-capture permission for its main task.

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What it does

Useful, focused capabilities

  • UTF-8 text and binary files
  • Base64 and Base64URL
  • Optional padding, line wrapping, and Data URLs
  • Strict decode validation
  • Binary result download

Browser compatibility

Requirements and honest fallbacks

JavaScript and the File API for optional local file input and download.

  • JavaScript
  • TextEncoder and TextDecoder
  • File API
  • download support

Questions people ask

Clear answers and limits

Is Base64 secure?

No. Anyone can decode it. Use encryption when confidentiality is required.

Why is the encoded output larger?

Base64 represents each three source bytes with four characters, usually adding about one third before headers or line breaks.

What is Base64URL?

It replaces + and / with URL-friendlier - and _. Padding may also be omitted depending on the consuming format.

Can binary output be previewed as text?

Only when the decoded bytes form valid UTF-8. Otherwise the page suppresses a misleading text preview and offers a file download.

Are Data URLs uploaded?

No. A Data URL is just a text representation created locally, but pasting it into another service can disclose its contents there.

How to use this tool

Encode or decode text and supported local file content as Base64 in this browser when you need to inspect or transform the representation. The route returns text or file content locally and does not upload it to an Aftermath conversion service. Review decoded output carefully before using it, especially when it may contain private, executable, or malformed data.

What to choose and what you get

What to choose

  • UTF-8 text or one local binary file for encoding
  • Base64, Base64URL, or a Data URL for decoding

Result

  • encoded Base64 text, decoded UTF-8 text, or a separately downloaded decoded binary file

Supported use

  • UTF-8 text and binary file bytes can round-trip through the selected mode.
  • Decoded bytes that are not valid UTF-8 remain a file result rather than a text preview.

Before you start

  • Does not encrypt, authenticate, or make Base64 content safe to execute.

Supported formats

  • Accepted formats: UTF-8 text, binary file, Base64, Base64URL, Data URL.
  • Output formats: Base64 text, UTF-8 text, binary file.

Browser support and permissions

  • Modern browser with JavaScript; clipboard, DOM, and download behavior varies by browser.
  • No camera, microphone, or screen permission is needed.

Choose the right settings

  • Use this route when the intended result is UTF-8 text ↔ Base64 or binary bytes ↔ Base64/file download.

Worked example

A short UTF-8 configuration string needs Base64 encoding for transport and then a round-trip decode check.

Starting facts

  • The input is not secret and stays in this browser.
  • Base64 changes representation but provides no encryption.

Observed operation: Encode the text locally, decode the result and compare the round-tripped characters before copying it.

Review the result: Verify the decoded value exactly matches the source and avoid placing sensitive content in an exposed payload.

Boundary: Base64 offers no confidentiality, integrity, authenticity or protection from anyone who can decode the value.

What you can do

Base64 encoder and decoder for UTF-8 text or binary files

If it does not work

  • Invalid alphabet, padding, or URL-safe input is rejected before decoding.
  • Decoded non-UTF-8 bytes are offered as a binary download without a misleading text preview.

Things to know

  • Base64 is an encoding, not encryption; review decoded bytes before opening or sharing them.

Privacy boundary

Entered text stays in the current browser session and is not sent to an Aftermath processing service. How local processing is verified.

What this tool verifies

Checks explicit UTF-8 text and binary-file Base64 modes, validates padding and URL-safe alphabets, and reports a text result or binary download.

Check before sharing

Base64 is reversible encoding, not encryption or authentication; a decoded file still needs safety review before opening.

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