RapidTables
rapidtables.com
Unit, number-base and colour conversions with the formula written underneath
No sign-upOn device
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fileinfo.com
Tells you what a mystery file extension is and what opens it.
A database of more than ten thousand file extensions: what the format is, who created it, which programs open it on Windows, macOS, Linux and mobile, and whether it is text or binary. It is the fastest way to answer 'what on earth is a .pkpass' before deciding whether to double-click it. It identifies formats; it does not convert, open or repair them.
Questions
Works the moment the page loads. No account, no email, no trial. Reference only — no conversion, no preview, and it cannot tell you what is inside your specific file.
Yes. FileInfo sends your input to its own servers to process it. That is fine for public material; for anything containing personal data, use one of the on-device tools instead.
Reference only — no conversion, no preview, and it cannot tell you what is inside your specific file.
Alternatives
Same category or same task, ordered by how closely they overlap.
rapidtables.com
Unit, number-base and colour conversions with the formula written underneath
convert.town
A pile of one-click converters that never upload the file
ezyzip.com
Opens and builds ZIP, RAR and 7z archives without uploading them
svgco.de
Traces a PNG or JPEG into a scalable SVG inside the browser
tinywow.com
A couple of hundred small file tools, free and with no account
transfonter.org
Turns a TTF or OTF into WOFF2 with the @font-face CSS written for you