Fix Extension

"Downloaded a bunch of archives, but extensions got changed to weird suffixes like .zip111, .rar001 and none of them will open..."

The Fix Extension rule reads the actual file content to determine the real file type, automatically fixing incorrect extensions. Especially useful for handling misnamed, disguised, or corrupted archive extensions.

This Feature Helps You

• ✅ Fix renamed archives: Change incorrect extensions like .zip111, .rar001 back to correct .zip, .rar
• ✅ Identify disguised files: Discover files with .txt extension that are actually .rar
• ✅ Batch fix damaged extensions: Fix dozens or hundreds of files with incorrect extensions at once
• ✅ Ensure files open properly: Let your decompression software correctly identify file types

Quick Start

1. Select files: Drag in files with incorrect extensions (recommend testing with a few archives first)
2. Add rule: Click "Add Rule" → Select "Fix Extension"
3. Preview and execute: Check preview results, confirm it's correct then click "Execute Rename"

Detailed Examples

Example 1: Fix Renamed ZIP Files

❌ Original: important_data.zip111

😫 Problem: Extension got 111 suffix added during download, can't open with decompression software

✅ Operation:

• Add "Fix Extension" rule
• Keep "Only fix archive extensions" option enabled (default)

✅ Result: important_data.zip

Why it works: The rule read the file header data, discovered it's actually a standard ZIP archive, so corrected the extension to .zip, now it can be decompressed normally.

Example 2: Identify Disguised RAR Files

❌ Original: secret_file.txt

😫 Problem: File looks like a text file, but opening shows gibberish, suspect it's a disguised archive

✅ Operation:

• Add "Fix Extension" rule
• Check "Only fix archive extensions"

✅ Result: secret_file.rar

Why it works: The rule identified it's actually a RAR archive by reading the file header's "magic number" (file type signature), automatically correcting the extension to .rar.

Example 3: Batch Fix Multiple Archives

❌ Original:

photo.7z001
video.tar002
music.gz111

😫 Problem: A batch of archives all got numeric suffixes added to their extensions, all unusable

✅ Operation:

• Select all files at once
• Add "Fix Extension" rule

✅ Result:

photo.7z
video.tar
music.gz

Why it works: The rule reads each file's header information, identifies the real type then batch corrects, solving all extension problems at once.

Parameters to Fill

Basic Parameters

Detailed Explanation

Only fix archive extensions (recommended to keep enabled)

Currently, type detection for non-archive files (like images, videos, documents) may not be accurate enough, so strongly recommend only using for fixing archive extensions.

Supported archive types:

• zip - ZIP archive
• rar - RAR archive
• 7z - 7-Zip archive
• tar - TAR archive file
• gz - GZIP compressed file
• iso - ISO image file
• xz - XZ compressed file
• bz2 - BZIP2 compressed file

If you want to fix extensions for other file types (at your own risk), you can uncheck this option.

Common Questions

Q: Why is it recommended to only fix archive extensions?

A: Because archive file format signatures are very clear (file headers have fixed "magic numbers"), detection accuracy is close to 100%. While detection for other file types (like images, videos) may not be accurate enough, with some risk of misjudgment. For safety, only archives are fixed by default.

Q: Will JAR files be corrected?

A: No. Although JAR files are essentially ZIP format, they have special purposes (Java packages), the rule automatically skips all .jar files and won't modify their extensions.

Q: Will it modify the actual file content?

A: Absolutely not. This rule only modifies the filename (extension part), without reading or modifying the actual file content. Your file content is completely safe.

Q: Why is it slow when processing many files?

A: Because the rule needs to read each file's header data to determine type, which requires disk I/O operations. To optimize performance, the rule has a built-in caching mechanism (caches up to 500 file detection results), so repeatedly processing the same files will be much faster.

Notes

Advanced Tips

Combine with Other Rules

• ✅ Combine with "Find Replace" rule: First use find replace to remove extra characters from filenames (like (1), _copy), then use fix extension rule to uniformly fix extensions
• ✅ Combine with "Remove Text" rule: First remove garbage prefixes or suffixes from filenames (like [Download], 111), then auto-detect correct extensions
• ✅ Combine with "Conditional Replace" rule: Filter files needing processing based on specific keywords in filename, then batch fix extensions

Typical Workflow

1. Step 1: Use "Remove Text" or "Find Replace" to clean garbage characters from filenames
2. Step 2: Use "Fix Extension" rule to auto-detect and fix correct extensions
3. Step 3: Use "Sequence" rule (if needed) to uniformly add numbering

What to Check Out Next

• Want conditional replacements? Try Conditional Replace Rule
• Need more powerful file processing? Check out JS Script Rule
• Want to batch add uniform numbering? Learn about Sequence Rule