How to Bulk Rename Files Using Regex
Renaming files one by one is one of the most tedious tasks in digital workflows. Whether you are organizing a photo library, standardizing document names, or preparing assets for a web project, the Regex Bulk File Renamer lets you rename hundreds of files in seconds using powerful pattern matching — with a live preview that shows exactly what will change before you commit.
Upload your files by dragging them into the upload zone. Any file type is supported — images, documents, audio, video, code files, or anything else. The tool reads each file's name but does not open or modify the file contents. Once loaded, every filename appears in a two-column preview table: original name on the left, proposed new name on the right.
Define your rename pattern using the Find and Replace fields. The Find field accepts full regular expression syntax, so you can match complex patterns. For example, the regex IMG_(\d{4})_(\d{4}) matches filenames like IMG_2026_0424 and captures the year and sequence number as groups. The Replace field can reference these groups: Photo_$1-$2 would produce Photo_2026-0424.
The preview table updates in real time as you type. If your pattern produces a conflict — two files getting the same new name — the conflict is highlighted in red. Adjust the pattern until all conflicts are resolved, then click Download ZIP to get all files with their new names.
Regular Expressions for File Renaming: A Quick Guide
Regular expressions (regex) are patterns that match text. For file renaming, they let you identify parts of a filename and rearrange, replace, or transform them. Here are the most useful patterns for bulk renaming:
Literal text: Type any text to match it exactly. IMG matches the string "IMG" anywhere in the filename.
Character classes: \d matches any digit (0-9). \w matches any word character (letters, digits, underscore). . matches any character. [a-z] matches any lowercase letter.
Quantifiers: \d+ matches one or more digits. \d{4} matches exactly four digits. \d{2,4} matches 2 to 4 digits. \w*? matches zero or more word characters (non-greedy).
Groups: Parentheses create capture groups. (\d+) captures a sequence of digits as group $1. (\w+)_(\d+) captures a word and a number as groups $1 and $2.
Anchors: ^ matches the start of the filename. $ matches the end. ^IMG only matches if the filename starts with "IMG".
Common rename patterns:
Remove date prefix: Find ^\d{4}-\d{2}-\d{2}_, Replace with (empty)
Extract numbers: Find [^\d]*(\d+)[^\d]*, Replace File_$1
Swap word order: Find (\w+)_(\w+), Replace $2_$1
Add prefix to all: Leave Find empty, set Prefix to Project_
Sequential numbering: Leave Find empty, set Prefix to #_ (produces 001_, 002_, etc.)
Why Live Preview Prevents Catastrophic Mistakes
The most dangerous moment in any batch rename operation is the moment you click "Apply." Without a preview, a typo in your regex pattern can silently rename every file to gibberish — or worse, to the same name, causing data loss. This is why professional file management tools always show a preview before executing changes.
The live preview table in this tool updates as you type, showing every proposed rename in real time. This means you can iteratively refine your pattern: type a partial pattern, check the preview, adjust, check again. Conflicts are highlighted immediately. Files that don't match your pattern are shown with an equals sign (=) instead of an arrow, so you can see which files are unaffected.
This approach eliminates the "rename anxiety" that comes with batch operations. You always know exactly what will happen before you download. And because the tool creates copies in a ZIP archive rather than modifying your original files, even an unexpected result is recoverable — your originals remain untouched.
Common Use Cases for Bulk File Renaming
Photo Library Organization: Camera-generated filenames like DSC_0482.jpg or IMG_4829.HEIC are meaningless. Rename them to include dates, events, or sequential numbers: Wedding_001.jpg, Wedding_002.jpg, etc.
Stock Photo Downloads: Stock photo sites generate filenames like shutterstock_284719362.jpg. Replace the stock site prefix with your project name: Campaign_Shoes_001.jpg.
Web Asset Preparation: Convert filenames to lowercase, replace spaces with hyphens, and remove special characters to create web-safe filenames: "My Photo (Final).jpg" becomes "my-photo-final.jpg".
Document Standardization: Enforce a consistent naming convention across a document library: add department prefixes, date stamps, or version numbers to hundreds of files at once.
Music Library Cleanup: Rename downloaded music files from random names to a consistent "Artist - Title.mp3" format using pattern matching on existing filename components.
Frequently Asked Questions
The tool uses JavaScript's native RegExp engine, which supports the full ECMAScript regular expression syntax. This includes character classes (\d, \w, \s), quantifiers (+, *, ?, {n,m}), groups and backreferences ((group) and $1), alternation (a|b), anchors (^, $), and lookaheads/lookbehinds. The case-insensitive flag can be toggled with the checkbox.
The # character is replaced with a zero-padded sequential counter that increments for each file: 001, 002, 003, and so on. For example, setting the prefix to "Photo_#" and the suffix to "" produces Photo_001, Photo_002, Photo_003. The counter starts at 001 and continues for every file in the batch, regardless of whether the regex matched.
No. Your original files are never modified. The tool reads each file into memory using the FileReader API and creates copies with new names inside a ZIP archive. Your originals remain exactly as they were on your device. This safety mechanism means you can always recover from an unexpected rename result.
The preview table highlights any duplicate proposed filenames in red with a warning icon. If two or more files would receive the same new name, you should adjust your pattern to differentiate them — for example, by including a counter (#) in the prefix or suffix. The tool does not auto-resolve conflicts to prevent silent data loss where one file overwrites another.
Yes. Leave the Find regex field empty and use only the prefix, suffix, and case transform options. With an empty Find field, no pattern matching occurs — the prefix is prepended, the suffix is appended, and any case transform is applied to the entire filename. This is the simplest way to add a common prefix or sequential numbering to a batch of files.