Base64 Encode & Decode

How to use Base64 Encode & Decode

1. Choose Encode or Decode.
2. Paste your text or Base64 string.
3. Copy the output, or use “Use result as input” to reverse it.

What Base64 is used for

Many protocols only handle plain text safely. Base64 converts any data into letters and digits so it can be embedded in JSON, HTML, CSS, email attachments or URLs. The cost is size: Base64 output is about 33% larger than the original.

Common places you will see it

• Data URLs: small images embedded directly in CSS or HTML (data:image/png;base64,…).
• HTTP Basic authentication headers, which carry “username:password” in Base64.
• JWT tokens, whose header and payload are URL-safe Base64 JSON.
• Email attachments (MIME) and API fields that carry file contents.

Standard vs URL-safe

Standard Base64 uses + and /, which have special meaning in URLs. The URL-safe variant swaps them for - and _ and usually drops the = padding. Use it for anything that goes in a query string, file name or JWT. This tool decodes both forms automatically.

Size, speed and limits

Base64 turns every three bytes into four characters, so output is roughly one third larger than the input. That overhead is why embedding large images as Base64 in a web page is rarely a good idea: the browser cannot cache them separately and the HTML grows. For small icons under a few kilobytes it can save a network request, which is the one case where it pays off.

This tool handles text of any reasonable size. If you need to encode a whole file such as an image, use our Image to Base64 tool, which reads the file bytes directly instead of treating them as text.

Why use this base64 encode & decode tool

• UTF-8 safe. Emoji and non-English characters encode and decode correctly.
• URL-safe option. Replaces + and / with - and _ and strips padding.
• Clear errors. Tells you when a string is not valid Base64.

Frequently asked questions

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