Free Online Regular Expression Tester
Regular expressions are one of the most powerful tools available to developers for searching, matching, and manipulating text. Whether you are validating user input, parsing log files, extracting data from documents, or performing complex find-and-replace operations, a well-crafted regex pattern can accomplish in a single line what might otherwise require dozens of lines of procedural code. However, writing correct regular expressions can be notoriously challenging. The compact syntax, with its special characters, quantifiers, character classes, and grouping constructs, can be difficult to read and even harder to debug when a pattern does not behave as expected. Our free online regex tester gives you instant visual feedback as you type, making it far easier to develop and refine your patterns.
Live Match Highlighting
As you type your regular expression pattern and test string, this tool instantly highlights every match directly within the text. Each matched portion of the input is visually distinguished so you can immediately see which parts of your string the pattern captures. This real-time feedback loop dramatically speeds up the process of building correct patterns because you do not need to run a separate script or switch between tools to verify your work. The match results panel shows the total number of matches found, along with the index position and value of each individual match, giving you complete visibility into how your pattern interacts with the test data.
Regex Flags and Options
Regular expression behavior can be modified using flags such as g for global matching, i for case-insensitive matching, m for multiline mode, s for dotAll mode, and u for Unicode support. This tool lets you specify any combination of flags so you can test exactly the behavior you need. Understanding how flags change pattern matching is essential for writing robust expressions, and being able to toggle them on and off in real time helps you learn how each flag affects the results. All processing is performed entirely in your browser using the native JavaScript RegExp engine, so your test data is never transmitted to any server, ensuring complete privacy and security.