APIVerve

Regex Tester API

POST
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Catch syntax errors and analyze regex structure before deploying.

Regex Tester tests regular expressions against input strings across operations like match, search, replace, and split. It reports compilation validity, syntax error details, execution timing, and structural pattern analysis.

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Request
POSTapi.apiverve.com/v1/regextester
Body
Verification
Format

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Example
{
  "status": "ok",
  "error": null,
  "data": {
    "pattern": "\\d{3}-\\d{2}-\\d{4}",
    "text": "My SSN is 123-45-6789 and my friend's is 987-65-4321",
    "flags": "g",
    "test_type": "test",
    "replacement": null,
    "is_valid_regex": true,
    "regex_info": {
      "pattern": "\\d{3}-\\d{2}-\\d{4}",
      "flags": {
        "global": true,
        "ignore_case": false,
        "multiline": false,
        "sticky": false,
        "unicode": false,
        "dot_all": false
      },
      "source": "\\d{3}-\\d{2}-\\d{4}",
      "last_index": 21,
      "pattern_length": 17,
      "complexity": "Medium"
    },
    "test_results": {
      "operation": "test",
      "result": true,
      "execution_time_ms": 0,
      "description": "Returns true if pattern matches anywhere in text, false otherwise"
    },
    "performance": {
      "iterations": 192,
      "total_time_ms": 0,
      "average_time_ms": 0,
      "performance_rating": "Excellent"
    },
    "pattern_analysis": {
      "contains_anchors": {
        "start_anchor": false,
        "end_anchor": false,
        "word_boundary": false
      },
      "contains_quantifiers": {
        "zero_or_more": false,
        "one_or_more": false,
        "zero_or_one": false,
        "specific_count": true,
        "range_count": false
      },
      "contains_groups": {
        "capturing_groups": 0,
        "non_capturing_groups": 0,
        "named_groups": 0
      },
      "contains_character_classes": {
        "predefined_classes": true,
        "custom_classes": false,
        "negated_classes": false
      },
      "contains_special_chars": {
        "wildcard": false,
        "pipe": false,
        "escape_sequences": 3
      }
    },
    "suggestions": [
      "Consider anchoring with ^ or $ if you need exact matches"
    ],
    "common_patterns": [
      {
        "name": "Email Address",
        "pattern": "^[\\w\\.-]+@[\\w\\.-]+\\.[a-zA-Z]{2,}$",
        "description": "Matches valid email addresses",
        "example": "[email protected]"
      },
      {
        "name": "Phone Number (US)",
        "pattern": "^\\(?(\\d{3})\\)?[-.\\s]?(\\d{3})[-.\\s]?(\\d{4})$",
        "description": "Matches US phone numbers in various formats",
        "example": "(123) 456-7890"
      },
      {
        "name": "URL",
        "pattern": "^https?:\\/\\/(www\\.)?[-a-zA-Z0-9@:%._\\+~#=]{1,256}\\.[a-zA-Z0-9()]{1,6}\\b([-a-zA-Z0-9()@:%_\\+.~#?&//=]*)$",
        "description": "Matches HTTP and HTTPS URLs",
        "example": "https://www.example.com"
      },
      {
        "name": "IP Address (IPv4)",
        "pattern": "^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$",
        "description": "Matches valid IPv4 addresses",
        "example": "192.168.1.1"
      },
      {
        "name": "Credit Card Number",
        "pattern": "^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|3[47][0-9]{13}|3[0-9]{13}|6(?:011|5[0-9]{2})[0-9]{12})$",
        "description": "Matches major credit card formats",
        "example": "4532123456789012"
      },
      {
        "name": "Social Security Number",
        "pattern": "^\\d{3}-?\\d{2}-?\\d{4}$",
        "description": "Matches SSN with or without dashes",
        "example": "123-45-6789"
      },
      {
        "name": "Date (MM/DD/YYYY)",
        "pattern": "^(0[1-9]|1[0-2])\\/(0[1-9]|[12][0-9]|3[01])\\/(19|20)\\d{2}$",
        "description": "Matches MM/DD/YYYY date format",
        "example": "12/31/2023"
      },
      {
        "name": "Time (24-hour)",
        "pattern": "^([01]?[0-9]|2[0-3]):[0-5][0-9]$",
        "description": "Matches 24-hour time format",
        "example": "14:30"
      },
      {
        "name": "Hexadecimal Color",
        "pattern": "^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$",
        "description": "Matches hex color codes",
        "example": "#FF5733"
      },
      {
        "name": "Strong Password",
        "pattern": "^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[@$!%*?&])[A-Za-z\\d@$!%*?&]{8,}$",
        "description": "At least 8 chars with uppercase, lowercase, digit, and special char",
        "example": "MyP@ssw0rd"
      }
    ],
    "regex_guide": {
      "basic_syntax": [
        {
          "symbol": ".",
          "description": "Matches any single character except newline"
        },
        {
          "symbol": "*",
          "description": "Matches 0 or more of the preceding character"
        },
        {
          "symbol": "+",
          "description": "Matches 1 or more of the preceding character"
        },
        {
          "symbol": "?",
          "description": "Matches 0 or 1 of the preceding character"
        },
        {
          "symbol": "^",
          "description": "Matches start of string"
        },
        {
          "symbol": "$",
          "description": "Matches end of string"
        },
        {
          "symbol": "|",
          "description": "OR operator"
        },
        {
          "symbol": "\\",
          "description": "Escape character"
        }
      ],
      "character_classes": [
        {
          "symbol": "[abc]",
          "description": "Matches any character in the set"
        },
        {
          "symbol": "[^abc]",
          "description": "Matches any character NOT in the set"
        },
        {
          "symbol": "[a-z]",
          "description": "Matches any lowercase letter"
        },
        {
          "symbol": "[A-Z]",
          "description": "Matches any uppercase letter"
        },
        {
          "symbol": "[0-9]",
          "description": "Matches any digit"
        },
        {
          "symbol": "\\d",
          "description": "Matches any digit (equivalent to [0-9])"
        },
        {
          "symbol": "\\w",
          "description": "Matches any word character [a-zA-Z0-9_]"
        },
        {
          "symbol": "\\s",
          "description": "Matches any whitespace character"
        }
      ],
      "quantifiers": [
        {
          "symbol": "{n}",
          "description": "Matches exactly n times"
        },
        {
          "symbol": "{n,}",
          "description": "Matches n or more times"
        },
        {
          "symbol": "{n,m}",
          "description": "Matches between n and m times"
        },
        {
          "symbol": "*?",
          "description": "Non-greedy: matches 0 or more (lazy)"
        },
        {
          "symbol": "+?",
          "description": "Non-greedy: matches 1 or more (lazy)"
        },
        {
          "symbol": "??",
          "description": "Non-greedy: matches 0 or 1 (lazy)"
        }
      ],
      "groups": [
        {
          "symbol": "(abc)",
          "description": "Capturing group"
        },
        {
          "symbol": "(?:abc)",
          "description": "Non-capturing group"
        },
        {
          "symbol": "(?<name>abc)",
          "description": "Named capturing group"
        },
        {
          "symbol": "(?=abc)",
          "description": "Positive lookahead"
        },
        {
          "symbol": "(?!abc)",
          "description": "Negative lookahead"
        },
        {
          "symbol": "(?<=abc)",
          "description": "Positive lookbehind"
        },
        {
          "symbol": "(?<!abc)",
          "description": "Negative lookbehind"
        }
      ],
      "flags": [
        {
          "flag": "g",
          "description": "Global - find all matches"
        },
        {
          "flag": "i",
          "description": "Case insensitive"
        },
        {
          "flag": "m",
          "description": "Multiline - ^ and $ match line breaks"
        },
        {
          "flag": "s",
          "description": "Dot matches newline characters"
        },
        {
          "flag": "u",
          "description": "Unicode mode"
        },
        {
          "flag": "y",
          "description": "Sticky - matches from lastIndex position"
        }
      ]
    }
  }
}

About the Regex Tester API

Regex Tester works by testing regular expressions against text and providing detailed results including matches, pattern analysis, performance metrics, and common pattern examples. Supports all standard regex flags and operations.

What people use it for

Pattern Development
Test and debug regex patterns before implementing them in production code to ensure correct matching
Data Validation
Validate regex patterns for input validation in forms, APIs, and data processing pipelines
Text Processing
Test regex patterns for text extraction, replacement, and parsing operations
Learning Tool
Learn regex syntax with detailed guides, common pattern examples, and real-time testing feedback

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON
Default REST response
XML
Markup format
YAML
Human-readable
CSV
Tabular export
Beta
GraphQL
Query language
New
MCP
For AI agents
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Other ways to use Regex Tester

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Questions.

Common questions about the Regex Tester API.

Read the docs →
Which plan fits 20,000 regex tests a month?
The Starter plan easily covers that volume. Running 20,000 tests uses 40,000 credits, fitting comfortably within Starter's monthly allowance of 100,000 calls. On Starter, testing works out to about $0.30 per 1,000 calls. The Free plan includes 100 calls per month for evaluation.
Is the regex performance analysis included on the Free plan?
No, multi-run performance benchmarking requires a paid subscription. The Free plan returns pattern validation, match results, execution time, structural analysis, and optimization suggestions, but omits the detailed performance metrics. Upgrading to the Starter plan or higher unlocks full performance data.
Which regex operations and flags can I test?
You can run test, match, search, replace, and split operations against your target string. Regex Tester supports standard flags including global, case-insensitive, multiline, dot-all, unicode, and sticky. For replace operations, you can supply custom replacement text in the request.
What does the response return if a pattern has a syntax error?
When a pattern fails to compile, the response sets the validity status to false and provides the compilation failure message in an error field. Instead of failing the request, Regex Tester also provides syntax suggestions to help you correct the invalid pattern.
Does it provide optimization tips for valid patterns?
Yes. Beyond matching text, the response includes a structural breakdown of your pattern's anchors, quantifiers, groups, and character classes. It provides optimization suggestions to improve pattern efficiency and includes a reference library of common regex patterns for comparison.
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