Encode any XLSX file to a Base64 string for embedding in JSON payloads, API requests, or email attachments. Free.
Free is enough for most one-off jobs. Pro raises the file and batch caps; Pro + Media unlocks GB-scale streaming and unlimited duration.
Larger files supported on Developer (5 GB CSV) and Enterprise (unlimited). All processing happens in your browser — files never reach a server.
Upload your Excel file
FileReader API reads the file bytes and encodes them as Base64
Copy the Base64 string for use in your API payload or config
0 bytes uploaded. Base64 Encoder runs entirely in your browser using SheetJS and ExcelJS. Your spreadsheets never leave your device.
Free tier: 5MB. Pro tier: 50MB. Base64 encoding increases file size by ~33%.
The reverse operation is on the roadmap. For now, paste your Base64 string into any online decoder or use atob() in a browser console.