What does the ;base64 flag mean?

It says the payload is Base64-encoded rather than percent-encoded. Without it, the data is URL-encoded text and is decoded with the same rules as any URL component.

Are data URIs bad for performance?

They save a request but add roughly a third to the payload size and can't be cached separately from the document that contains them. They are a good fit for tiny assets, a poor one for anything large.

Can a data URI be dangerous?

Yes. data:text/html and script-bearing SVG payloads have been used for phishing and XSS, which is why browsers block top-level navigation to data: URLs. Inspect them here rather than opening them.

Data URI Parser

Split a data: URI into its MIME type, encoding and decoded payload.

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RAW INPUT

DECODED

Output appears here as you type — decoded on your device.

Input is processed on your device. Nothing you paste is sent anywhere.

What is the Data URI Parser?

A data URI parser breaks a data: URL into its three parts — MIME type, optional parameters such as charset or ;base64, and the payload — then decodes the payload so you can see what is embedded inline.

A data URI (RFC 2397) embeds a whole resource inside a URL: data:[<mediatype>][;base64],<data>. It is how small icons, inline SVGs, fonts and preview images get inlined into HTML and CSS without a separate request. The trade-off is size — Base64 inflates the payload by a third — and cacheability, since inlined data can't be cached independently.

Data URIs also appear in security work. Phishing pages have used data:text/html payloads to render an entire fake login form from a URL, and malicious SVGs can carry script. Parsing the URI locally lets you read exactly what is inside without rendering it.

This parser reports the declared MIME type, whether the payload is Base64 or percent-encoded, the decoded byte length, and the decoded content itself.

Data URI Parser at a glance

Specification: RFC 2397
Syntax: data:[<mediatype>][;base64],<data>
Default type: text/plain;charset=US-ASCII when omitted
Overhead: +33% when Base64-encoded

How to use the Data URI Parser

1Paste the full data: URI, starting with the data: scheme.
2Read the parsed MIME type, encoding flag and decoded payload.
3Copy the decoded content, or check the byte size before inlining it in production.

When you would reach for it

Extracting an inline image or SVG out of HTML or CSS source.
Checking what a data: link in a suspicious email or page actually contains.
Measuring how much weight an inlined asset adds to a stylesheet.

Data URI Parser — frequently asked questions

Last reviewed 25 July 2026 · questions or corrections: contact@decoder.tools