Convert CSV to Base64

Base64 packs 3 input bytes into 4 output characters (each character carries 6 bits). That’s a fixed 4/3 expansion – about 33%. Plus up to 2 characters of = padding at the end to round out to a multiple of 4. The overhead is the price of making arbitrary bytes safe for text-only channels.

Yes. Base64 operates on bytes, not structure. Newlines (0x0A), carriage returns, commas, quotes, tabs – every byte goes in, every byte comes back out on decode. A round-trip is guaranteed lossless, which is exactly why Base64 is used to ship CSV through channels that would otherwise mangle line endings or strip special characters.

Use URL-safe whenever the result ends up in a URL path, query string, filename, or JSON Web Token. Standard Base64’s + and / get percent-encoded in URLs (to %2B and %2F), which doubles the effective overhead. URL-safe swaps them for - and _ so the string drops in cleanly.

RFC 2045 (MIME) requires Base64 bodies in email to break every 76 characters with a CRLF so legacy mail servers don’t choke on long lines. This tool uses LF to stay readable on screen; add r yourself if you’re targeting a strict MIME implementation. Use 64 for PEM blocks (certificates, private keys).

Yes. Input is encoded via TextEncoder to UTF-8 bytes before Base64 runs. So 日本 (6 UTF-8 bytes) encodes to 8 Base64 characters, and a 4-byte emoji encodes to roughly 6 characters plus padding. The deprecated unescape()/btoa() trick is avoided entirely.

Mostly for Excel. When you decode the Base64 and save the result as a .csv, Excel on Windows treats files without a BOM as ANSI (cp1252), which mangles non-ASCII characters. A leading EF BB BF tells Excel “this is UTF-8” and fixes the encoding detection.

Yes. Prefix with data:text/csv;base64, and you have a self-contained URL that downloads your CSV when clicked. Prefer URL-safe Base64 or use standard and expect the browser to handle +//. For very large CSVs browsers cap data URL length at a few MB.

Base64 outputs 4 chars per 3 input bytes. If the input byte length isn’t a multiple of 3, Base64 appends one or two = to pad to 4. Length of = padding = (3 - inputBytes % 3) % 3. Strip-padding toggle removes them – the decoder can reconstruct from length alone.

Use our Base64-to-CSV decoder (or any Base64 decoder). Since encoding is pure byte work, the decoded output will be byte-identical to your original CSV, including newlines, quoting, and BOM if you prepended one. Nothing is lost.

Yes to all three. The encoder runs entirely in your browser with TextEncoder + btoa. Your CSV is never uploaded, never logged, never stored. Load the page once, disconnect from the internet, and it keeps working indefinitely.