Remove special characters, keeping what you actually need

Whatever the system rejecting your text says counts, which is why this page asks rather than assumes. A web form usually means anything that is not a letter, a digit or a space. A filename means a specific handful — the slash, the colon, the question mark and a few others that the operating system reserves. An older database means anything outside the first 128 characters, which includes every accented letter. A spreadsheet import often means only the invisible control codes. The defaults here keep letters, digits, spaces, line breaks and other alphabets, and everything else has a switch.

Because ø has no accent to strip — it is a letter in its own right, not an o wearing something. Stripping accents works by splitting a letter into its base and its mark and throwing the mark away, which handles é, ñ, ü and about 500 others. But ø, ß, æ, ł, đ and þ are stored as single indivisible characters, so the split finds nothing and they come through untouched. This page carries a table of the 25 letters in that position and maps them by hand: ø becomes o, ß becomes ss, æ becomes ae, so Ærøskøbing comes out as AEroskobing rather than unchanged.

Whole emoji go, including the parts you cannot see. A single emoji is often several characters glued together: a family picture is four separate figures with three invisible joiners holding them in place, and choosing a skin tone quietly appends a second character behind the one you picked. Removing only the visible pieces leaves the joiners behind as invisible junk, which is how text ends up with characters in it that nothing can account for. Every piece is recognised as belonging to the emoji and removed together, and if you switch emoji to be kept, the joiners are kept too so the family does not split into four separate people.

Turn accents to plain letters, leave digits and spaces on, and type an underscore, a hyphen and a dot into the spare-these field so the extension survives. That leaves you a name that will move between Windows, macOS and Linux without an argument, since the characters those systems reserve are all symbols or punctuation. If you want the spaces gone as well, untick spaces — or use a slug instead, which is the same idea with hyphens as the separator.

Only if you tell it to. Letters from other alphabets are kept by default, on the grounds that a letter is a letter — Привет and 日本語 are words, not symbols, and removing them silently would be a nasty surprise for anyone cleaning a multilingual list. Untick that box when your destination genuinely accepts Latin letters only, which is the case for some older systems and most web addresses.

They are the leftovers of 1960s teleprinter conventions — null, bell, form feed, vertical tab — and they are always removed here because nothing you write by hand contains one. They arrive in exports from old databases, in files that have been through a broken encoding conversion, and in anything copied out of a terminal. They usually render as a small box or as nothing at all, and they are a common cause of an import failing on a row that looks perfectly ordinary.

Because currency is a switch of its own and it is off by default, since most systems asking for special characters to be removed do not want a euro sign either. Tick the currency box and $, €, £, ¥ and the rest survive. The maths box is separate and covers +, =, <, >, %, ° and the times and division signs, which are classified as symbols too and so are removed by the same default.