How to convert an excel workbook to a base64-encoded string
- Step 1Drop your Excel file — Upload any file you want to Base64-encode. Works with .xlsx, .xlsm, .pdf, and any other format.
- Step 2Encode — FileReader.readAsDataURL() converts the file to a Base64 data URI. The Base64 string is extracted and displayed.
- Step 3Copy the Base64 string — Copy the encoded string to clipboard for use in API requests, JSON payloads, or email attachments.
Frequently asked questions
Can I decode Base64 back to a file?+
Not yet. Base64 decoding back to a downloadable file is on the roadmap.
Is there a file size limit?+
Free tier: 5 MB. Pro tier: 50 MB. Very large Base64 strings (10+ MB) may be slow to display in the text preview.
Does Base64 encoding increase file size?+
Yes. Base64 adds approximately 33% overhead. A 1 MB Excel file becomes about 1.33 MB as a Base64 string.
Privacy first
Every JAD Excel tool runs entirely in your browser using SheetJS and ExcelJS. Your spreadsheets, formulas, and data never leave your device — verified by zero outbound network requests during processing.