Lowercase converter
Transformed in your browser · nothing is uploaded
Converts every letter to lowercase, accented and non-Latin ones included, and leaves digits and punctuation alone. It is the un-shout for a document typed in capitals, and the first step in almost any comparison of two pieces of text.
How to use the lowercase converter
Folding the case is what makes two pieces of text comparable: Apple and apple are different strings to a database, a Set or a URL router until one of them is lowercased. That is why tags, slugs and lookup keys are lowercased on the way in rather than on the way out. Email addresses are the everyday example — the domain half is case-insensitive by the standard, while the part before the @ technically is not, even though virtually every provider treats it as if it were, which is why deduplicating a mailing list starts with a lowercase pass.
The mapping used here is the Unicode default one, not a language-specific one, and two cases are worth knowing. The Turkish dotted capital İ lowercases to a plain i followed by a separate combining dot: two code points that look like one letter and no longer match a typed i. And the Kelvin sign K, a different character from the letter K, lowercases to an ordinary k, so two distinct characters fold into one. Lowercasing is a normalising step, in other words, not a reversible transform: some information goes and does not come back.
Questions
Yes; É becomes é, Ø becomes ø, Σ becomes σ. Only letters change; digits and punctuation are untouched.
No. German ß uppercases to SS, which lowercases back to ss, and several characters fold together on the way down.
It became an i plus a separate combining dot — two code points rendered as one letter. The remove-accents tool strips the mark and leaves a plain i.
Apple and apple are different strings to everything downstream. Folding the case first is what makes a lookup, a tag or a slug behave.
You can, and you should not. It lowercases identifiers, string contents and attribute values along with everything else.
No practical one. The conversion runs in this tab, so nothing is uploaded and nothing is stored.