Data URI Decoder

How to use

1. 1Paste a data: URI into the input box. Both Base64 (with ;base64) and percent-encoded forms are accepted, with or without a declared MIME type.
2. 2Click Open .txt file to load a saved data: URI from disk, or pick one of the sample buttons (Plain text, JSON, CSS, SVG, PNG) to try the decoder.
3. 3Read the Summary panel for the MIME type, parameters, encoding, charset, and the decoded byte size.
4. 4Switch between Preview (image, audio, video, PDF), Text (decoded with the declared charset), Hex dump (offset + bytes + ASCII), and Raw bytes tabs.
5. 5Click Download to save the decoded payload with the right extension, or copy the Normalized data URI to paste a cleaned version back into HTML, CSS, JSON, or SVG.

About this tool

Data URI Decoder parses any RFC 2397 data: URI directly in your browser and shows you exactly what it contains. Paste a data: URL from a stylesheet, a JSON response, an inline SVG, an HTML attribute, a Markdown image, or a network capture, and the tool surfaces the MIME type, the parameters (charset, name, anything else after a semicolon), whether the payload is Base64 or percent-encoded, and the decoded byte size in both human-friendly and exact-byte form. The preview adapts to what the URI actually carries: images (PNG, JPG, GIF, WEBP, AVIF, BMP, ICO, SVG) render in a checkered canvas so transparency is visible; audio clips get a native HTML5 audio player; video clips get a native player with controls; PDFs load in an inline iframe viewer; SVG renders both as an image and as readable source on the Text tab; JSON, HTML, CSS, JavaScript, XML, Markdown, YAML, and other textual MIMEs decode through the TextDecoder API using the declared charset and show as monospace text with a copy button. A classic hex dump tab is always available with 16 bytes per row, offsets on the left, and an ASCII gutter on the right, the same format xxd and Vim use. The Raw bytes tab shows the first 4 KB as a stream of hex pairs for quick inspection. A single Download button writes the decoded payload to disk with the correct file extension inferred from the MIME type, so a data:application/pdf URI becomes decoded.pdf and a data:image/png URI becomes decoded.png. The Normalized data URI block re-emits the input with the detected MIME, cleaned Base64 padding, and stable parameter order, which is useful when one tool emitted a malformed URI and another tool refuses to parse it. The parser follows RFC 2397: when no media type is declared the default is text/plain, when ;base64 is missing the payload is percent-decoded, and quoted parameter values (RFC 2045) are unwrapped. Useful when you need to inspect an inline CSS background-image, debug a webhook that base64-encodes a PDF attachment, audit a Markdown export for embedded images, recover a file from a frontend memory dump, sanity-check the data: URLs an LLM generated, see what a screenshot pasted into chat actually contains, or just read the JSON inside a data:application/json URL. Decoding runs entirely in your browser using atob, TextDecoder, and Blob APIs; the data URI you paste never leaves your device.

Free to use. Works in your browser. No signup, no login.