This page finds U+FEFF (byte order mark) anywhere in your text and removes it. The sample below hides one at the start of a JSON document. Everything runs in your browser — nothing is uploaded.
A marker some editors write at the very start of a UTF-8/UTF-16 file. In UTF-8 it's the three bytes EF BB BF. It's invisible in most editors, and when a tool mishandles the encoding it shows up as the tell-tale mojibake .
Files saved as "UTF-8 with BOM" (classic Windows Notepad, some IDE defaults), CSV files exported by Excel, and string concatenation that glues whole file contents together — which is how a BOM ends up in the middle of text, where it acts as a deprecated "zero width no-break space".
JSON.parse fails with Unexpected token '\uFEFF'. The first CSV column comes out named \ufeffid instead of id, silently breaking lookups. A BOM before #!/bin/bash stops the shebang from working (cannot execute: required file not found). In PHP it triggers the classic headers already sent error.
Check a file with file yourfile (it reports "with BOM") or hexdump -C yourfile | head -1 (look for ef bb bf). Strip it with sed -i '1s/^\xEF\xBB\xBF//' file — or paste the text above and copy the cleaned output.
Guides for the common cleanup jobs — what the source puts into your text, exactly what it breaks, and the tool preloaded with a demonstration:
AI-generated text · Text copied from Word / Google Docs · Text copied from a PDF · Pasted code that won’t run · CSV & spreadsheet data · Invisible watermarks · Many files at once (batch)
Dedicated pages for the usual suspects — what each one is, where it sneaks in from, the exact errors it causes, and how to find it in your editor:
Zero-width space (U+200B) · Non-breaking space (U+00A0) · Byte order mark (BOM) (U+FEFF) · Soft hyphen (U+00AD) · Smart quotes · Em dash (U+2014) · Narrow no-break space (U+202F) · Ideographic space (U+3000) · Zero-width joiner (U+200D) · Zero-width non-joiner (U+200C) · Word joiner (U+2060) · Right-to-left override (U+202E) · Left-to-right mark (U+200E) · Line separator (U+2028) · Variation selector-16 (U+FE0F) · Object replacement character (U+FFFC) · Hangul filler (U+3164) · Braille pattern blank (U+2800) · Ligatures · Minus sign (U+2212)
Страницы на русском — те же инструменты с переведёнными правилами и примерами под задачу:
Невидимые символы в тексте · Убрать невидимые символы · Почистить текст нейросети · Неразрывные пробелы в числах · Текст из Word · Код не запускается