Sequence Gap Checker – Find Missing Numbers in Sequential Files for Windows

Overview of Sequence Gap Checker

A Windows utility that scans sequentially numbered files and quickly finds missing numbers in file name sequences.

• Quickly find missing numbers in file sequences
  Detect missing files such as pic003.jpg in a sequence containing pic001.jpg, pic002.jpg, and pic004.jpg.
• Automatic file name pattern detection
  Select a target folder and file extension, and Sequence Gap Checker can automatically detect the prefix, suffix, and numbering format used by sequential files.
• Supports zero-padded and variable-length numbering
  Check fixed-width sequences such as 001, 002, 003… as well as non-padded sequences such as 1, 2, …9, 10, 11….
• Scan subfolders recursively
  Search the selected folder and all of its subfolders, checking each folder independently for gaps in numbered file sequences.
• Choose between automatic and manual pattern settings
  Use automatic detection for convenience, or manually specify the prefix, suffix, file extension, and number format when you need precise control.

Supported OS

Windows 11 / Windows 10 / Windows 7

Screenshot

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Notes (Terms of Use)

• This software is provided as freeware. It may be used free of charge for personal or commercial purposes.
• Please read and agree to the terms of use before using this software.
• Bug reports and feature requests are welcome via email.

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FAQ

When is Sequence Gap Checker useful?

Sequence Gap Checker is useful when you need to check a large number of sequentially numbered files for missing numbers.

For example, if you have image files, scanned documents, exported video frames, backup files, or measurement data saved with names such as:

pic001.jpg, pic002.jpg, pic003.jpg, pic005.jpg …

Sequence Gap Checker can quickly detect that pic004.jpg is missing.

It can also scan subfolders, making it useful when you need to check large collections of sequential files spread across many folders. With automatic file name pattern detection, the software can identify the numbering pattern and look for gaps without requiring you to manually specify the prefix, suffix, or number of digits.

It is especially helpful when you want to efficiently find missing files that would be easy to overlook manually, or when you want to verify that file copying, saving, exporting, or other batch processing has completed correctly.

What types of file names are supported?

Sequence Gap Checker can check files that contain sequential numbers anywhere within the file name.

For example, it supports file names such as:

• pic001.jpg
• image_0001.png
• photo12_backup.webp
• scan_005_page.tif

In manual mode, you can specify the text before the sequence number, the text after it, the file extension, the number of digits, and other settings.

You can also use automatic file name pattern detection. This feature automatically finds numbered sequences in files with the specified extension. If multiple numbering patterns exist in the same folder, Sequence Gap Checker can detect and check each pattern separately.

What is the difference between automatic detection and manual mode?

Automatic detection is designed for convenience, while manual mode is better when you want precise control over the matching conditions.

With automatic file name pattern detection, you specify the target folder, file extension, and other basic settings, and Sequence Gap Checker automatically determines the text before and after the sequence number and the numbering format. This is useful when you are not sure how the files are named or when you want to check multiple numbering patterns at once.

In manual mode, you can specify the prefix, suffix, file extension, number of digits, minimum value, and other settings yourself. This is ideal when you already know the exact file name format and want to check only a specific sequence.

You can switch between automatic detection and manual mode depending on your needs.

Change Log

ver 1.0.0 (August 12, 2026)

• Initial release