Extract Substring
Grab part of some text — by character index (negatives count from the end) or everything between two delimiters. Runs in your browser; nothing is uploaded.
About this tool
Extract Substring pulls a portion out of a piece of text, two ways:
- Index mode — give a start and (optional) end character position. Positions are 0-based, the end is exclusive, and negative numbers count from the end (Python-style). Leave the end blank to go to the end of the string. Indexing is by character, so it's safe with accents and emoji.
- Delimiters mode — give a start delimiter and an end delimiter, and
get back every chunk found between them (e.g. everything inside
[...], or between<b>and</b>).
Pick the mode from the dropdown and fill in the fields it uses. Everything runs locally in your browser via WebAssembly — your text is never uploaded.
Examples
- Index:
start=0, end=5on "hello world" →hello;start=-5→world. - Delimiters:
[/]on "a[1]b[2]c[3]" →1,2,3.
FAQ
What happens if my start or end index is out of range?
Nothing breaks — indices are clamped to the text length. end=999 on an
11-character string just means "to the end", and if the resolved start ends up
at or past the end you get an empty result rather than an error.
How do negative indices work?
Python-style: they count back from the end. On hello world, start=-5 gives
world, and start=0, end=-6 gives hello. Leave the end blank to take
everything from the start index to the end of the string.
Are the delimiters regular expressions?
No — they're matched as literal text, so [, </b> or " need no
escaping. The tool returns every non-overlapping chunk between the pair,
one per line, scanning left to right; if the pair never matches you get
"No matches between the delimiters." Both delimiters are required in this mode.
Does the index count bytes or characters?
Characters (Unicode code points), never bytes — so é, 漢 or 👍 each count
as one and slicing can't cut a character in half. Only multi-code-point
sequences like family emoji or flag emoji occupy more than one index position.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool extract-substring "The source text…"New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/extract-substring/?text=The%20source%20text%E2%80%A6&mode=index&start=0&end=5&start_delim=%5B&end_delim=%5DMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.