Grep Online — Browser Pattern Search, Regex, Free
Search any text for matching lines using regex or plain string. Like grep, in the browser. Highlights, counts, no install.
About Grep Tool
Grep is the classic Unix tool for searching plain text — given a pattern (literal or regex), it returns the lines that match. The ZTools Grep Tool brings the same capability to the browser: paste any text, pattern (literal substring or JavaScript regex), and get the matching lines highlighted plus a match count. Useful when you don't have a terminal, or when the input is in your clipboard rather than a file. Supports case-insensitive matching, inverse match (lines that DON'T contain the pattern), context lines (-A / -B / -C), whole-word match, and line-number prefix.
Use cases
- Filter a paste of log lines. Shell access not available; you have a 5,000-line log paste from a colleague. Grep for ERROR — see only the failures.
- Find usages in pasted code. Pasted a 1000-line file from a screen-share. Grep for "TODO" or a specific function name — instant locator.
- Filter CSV rows by pattern. Need rows where the email column contains "@gmail.com". Grep with regex — cleaner than loading into a spreadsheet.
- Test a regex. Paste sample text, enter the pattern, see what matches. Faster feedback loop than running grep in a shell repeatedly.
How it works
- Paste input. Up to several MB of text. Tool stores in memory only.
- Enter pattern. Literal substring (default) or JavaScript regex (toggle). Regex flags: i (case-insensitive), m (multiline), u (unicode).
- Configure mode. Inverse (-v: lines NOT matching), word boundary (-w), max results, context before / after / around matched lines.
- Read output. Matching lines with optional line-number prefix. Highlight on the matched span. Match count shown at the top.
Examples
Input: Pattern: ERROR; input: 1000 log lines
Output: Output: only lines containing "ERROR", line numbers prefixed, count e.g. 47 matches.
Input: Regex: ^\\d{4}-\\d{2}-\\d{2}
Output: Returns only lines starting with a YYYY-MM-DD date — useful for filtering log entries by date format.
Input: Inverse match: pattern "DEBUG", flag -v
Output: Returns all lines that DON'T contain DEBUG — drop the noisy debug lines.
Input: Context: -C 2 around match
Output: Each match shows the 2 lines before and 2 lines after — better situational context for log triage.
Frequently asked questions
Is this real grep or a JavaScript imitation?
JavaScript imitation. Most flags work the same way. Differences: JS regex syntax (no PCRE backreferences in some engines), no file I/O, no recursive directory grep.
PCRE vs JS regex?
JavaScript regex. Look-behind requires modern browsers; named groups supported. For PCRE-only features (recursive patterns, conditionals), use a desktop tool.
How big an input can it handle?
Several MB is fine. 100+ MB causes the browser to lag — use a CLI grep instead.
Privacy?
Input never leaves the browser. No upload, no logging.
Can it grep across multiple files?
Single input only. For multi-file search, use ripgrep or VS Code search.
Pro tips
- Use word-boundary mode (-w) when searching for short identifiers — avoids matches inside longer words.
- Test regex against a few sample lines first — incremental feedback beats running on the full file with a wrong pattern.
- Inverse match (-v) is the fastest way to drop noise (DEBUG lines) and focus on signal (WARN/ERROR).
- For huge inputs (>10 MB), prefer ripgrep CLI — designed for speed and handles GBs gracefully.
Reviewed by Ahsan Mahmood · Last updated 2026-05-06 · Part of ZTools.
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