Grep Pattern Tester API

Test exact strings or regex patterns against any input text. Live filtering with match highlighting, context lines, and invert match. 100% client-side.

The Grep Pattern Tester is also available as a free REST API. Send a POST request with a JSON body to https://dot.tools/api/tools/grep — no authentication, no API key, CORS enabled. Successful calls return { "ok": true, "result": { … } }; failures return HTTP 400 or 422 with an error body.

Request body

Field	Type	Required	Description
`text`	string	required	The input text to search through.
`pattern`	string	required	The search pattern — either a literal string or a regular expression.
`mode`	"exact" \| "regex"	required	Whether the pattern is a literal string or a regex.
`position`	"contains" \| "prefix" \| "suffix" \| "exact"	required	Match position for exact mode: contains, prefix, suffix, or exact match.
`caseInsensitive`	boolean	required	Ignore letter case when matching.
`wholeWord`	boolean	required	Match complete words only, not substrings.
`invertMatch`	boolean	required	Return non-matching lines instead of matching lines.
`keepBlankLines`	boolean	required	Preserve empty lines in results.
`maxHits`	number	required	Maximum number of match results to return.
`linesBefore`	number	required	Number of context lines before each match.
`linesAfter`	number	required	Number of context lines after each match.
`trimWhitespace`	boolean	required	Remove leading/trailing whitespace from lines.
`flags`	object	required	Regex flags (only used in regex mode).

Response

Field	Type	Required	Description
`matches`	object[]	required	Matched lines with highlight ranges.
`totalLines`	number	required	Total number of lines in input.
`matchCount`	number	required	Number of matched lines.
`nonMatchCount`	number	required	Number of non-matched lines.

Example request

curl -X POST https://dot.tools/api/tools/grep \
  -H 'Content-Type: application/json' \
  -d '{
  "text": "[2024-01-15 08:23:01] INFO  Server started on port 8080\n[2024-01-15 08:23:02] INFO  Database connection established\n[2024-01-15 08:24:15] WARN  Request timeout on /api/users (3000ms)\n[2024-01-15 08:25:03] ERROR Failed to authenticate user: invalid token\n[2024-01-15 08:25:04] ERROR Database query failed: connection reset\n[2024-01-15 08:26:12] INFO  User login successful: user_id=4521\n[2024-01-15 08:27:45] WARN  High memory usage detected: 89.2%\n[2024-01-15 08:28:01] ERROR Critical: Disk space below 5% on /dev/sda1\n[2024-01-15 08:28:33] INFO  Cache cleared successfully\n[2024-01-15 08:29:55] ERROR Network unreachable: backup server 10.0.1.50\n[2024-01-15 08:30:12] INFO  Scheduled task completed: email_digest\n[2024-01-15 08:31:00] WARN  SSL certificate expires in 14 days\n[2024-01-15 08:32:22] ERROR Permission denied: /var/log/secure\n[2024-01-15 08:33:01] INFO  Health check passed\n[2024-01-15 08:34:45] ERROR Service unavailable: payment gateway timeout",
  "pattern": "ERROR",
  "mode": "exact",
  "position": "contains",
  "caseInsensitive": false,
  "wholeWord": false,
  "invertMatch": false,
  "keepBlankLines": false,
  "maxHits": 100,
  "linesBefore": 0,
  "linesAfter": 0,
  "trimWhitespace": false,
  "flags": {
    "global": true,
    "multiline": false,
    "dotall": false,
    "unicode": false
  }
}'

Sample response

{
  "ok": true,
  "result": {
    "matches": [
      {
        "line": 4,
        "text": "[2024-01-15 08:25:03] ERROR Failed to authenticate user: invalid token",
        "ranges": [
          [
            22,
            27
          ]
        ]
      },
      {
        "line": 5,
        "text": "[2024-01-15 08:25:04] ERROR Database query failed: connection reset",
        "ranges": [
          [
            22,
            27
          ]
        ]
      },
      {
        "line": 8,
        "text": "[2024-01-15 08:28:01] ERROR Critical: Disk space below 5% on /dev/sda1",
        "ranges": [
          [
            22,
            27
          ]
        ]
      },
      {
        "line": 10,
        "text": "[2024-01-15 08:29:55] ERROR Network unreachable: backup server 10.0.1.50",
        "ranges": [
          [
            22,
            27
          ]
        ]
      },
      {
        "line": 13,
        "text": "[2024-01-15 08:32:22] ERROR Permission denied: /var/log/secure",
        "ranges": [
          [
            22,
            27
          ]
        ]
      },
      {
        "line": 15,
        "text": "[2024-01-15 08:34:45] ERROR Service unavailable: payment gateway timeout",
        "ranges": [
          [
            22,
            27
          ]
        ]
      }
    ],
    "totalLines": 15,
    "matchCount": 6,
    "nonMatchCount": 9
  }
}

Use the free Grep Pattern Tester in your browser, read the Grep Pattern Tester guide, or import the full OpenAPI specification.