Read any user-selected local file as exact bytes and build a copyable data URL with its browser-reported MIME type and RFC 4648 Base64 payload. Perfect for embedding images, fonts, or documents directly in HTML, CSS, or JavaScript without a server. Supports drag-and-drop and file picker workflows.
Base64 tools
Base64 data URI
The data URI will appear here.
Convert a file to data:[mime];base64,… entirely in browser memory, preserving bytes while making the roughly one-third size expansion and MIME fallback explicit.
Complete a verifiable File to Base64 Data URL Converter workflow in this browser.
Step 1
Click the drop area and select the exact file whose bytes should be represented.
Step 2
The input panel shows the chosen filename after FileReader has loaded it.
Step 3
Verify the media type before the comma; an unknown browser type becomes application/octet-stream.
Step 4
Base64 expands the payload to about four characters for each three source bytes, plus the data URL prefix.
Step 5
Use the result for a receiver that explicitly accepts a data URL and can tolerate its size.
Consequence: Base64 expansion, parsing, and duplicate in-memory copies create a much larger payload and can delay rendering.
Fix: Use a normal file URL or upload channel for large assets; reserve data URLs for small, intentional embeds.
Consequence: The MIME value can be empty or based on filename/platform metadata and does not prove the bytes match it.
Fix: Validate file signatures in the consuming system when type matters.
Consequence: The data: prefix and comma cause the receiver to reject or misdecode it.
Fix: Confirm the contract and remove the prefix only when the receiver explicitly wants the payload alone.
Convert a small fixture, verify MIME and payload, then paste the data URL into markup only if the size is acceptable.
Send text to the UTF-8 encoder and arbitrary file bytes to this converter.
The five ASCII bytes spell Hello; RFC 4648 encodes them as SGVsbG8= and RFC 2397 places that payload after the text/plain data URL prefix.
It returns a complete data URL: data:, a MIME type, ;base64,, and the encoded payload.
Yes, the byte conversion is type-agnostic, subject to browser memory; the tool does not interpret or validate the format.
The selected File had no browser-reported type, so the tool uses the generic binary MIME fallback.
Base64 represents each three bytes with four characters, before adding the data URL prefix.
No. FileReader accesses the file only after your explicit selection and processes it inside the tab.
No. It is one-way from local file to data URL; use a dedicated binary decoder for the reverse operation.
The selected file is read into this tab with FileReader and converted by browser JavaScript. It is not uploaded to TetraBrain Desk. Offline conversion works once static assets are cached, but the full file and expanded string remain in volatile tab memory until cleared or the page closes.
