This page finds U+3000 IDEOGRAPHIC SPACE (the full-width CJK space) and converts it to a regular space. The sample hides one in Python indentation. Everything runs in your browser — nothing is uploaded.
The full-width space used in Chinese, Japanese and Korean typesetting — as wide as a CJK character, so columns of mixed text align. In CJK prose it's completely normal. In code and data it's a trap.
Typing a space while an IME (Japanese, Chinese or Korean input method) is in full-width mode — an extremely easy slip that puts U+3000 where U+0020 was intended. Also copied from CJK documents, spreadsheets and web pages.
Python rejects it with SyntaxError: invalid non-printable character U+3000 (it is not valid indentation); other languages produce their own "invalid character" errors. Shells split arguments wrong or fail with command not found. Form validators reject "blank" fields that contain it, string trimming often misses it, and spreadsheet lookups fail on values padded with it.
Many editors show it as a wide blank box; VS Code highlights it via unicode highlighting, and you can regex-search \u3000. Command line: grep -rP '\x{3000}' . — or paste the text above: it's marked with a dot and converted to a regular space in the 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