Lowercase Filenames
Lowercase Filenames calls toLowerCase() on each entire filename, including its extension, then downloads renamed-files.zip. It does not rename originals, preserve original casing in any component, use a user-selected locale, transliterate characters, validate filesystem rules, or resolve collisions such as Readme and README becoming the same target name.
Runs locally — files stay on your deviceIs the extension lowercased too?
Yes. The complete filename is converted.
Case conversion can collapse distinct names
Case-sensitive filesystems may allow names that differ only by case. Lowercasing a batch can therefore create duplicate target names.
How it works
JavaScript String.toLowerCase transforms every File.name and JSZip packages each file under that result.
Key concepts
Whole name changes
Both basename and extension are lowercased.
References stay unchanged
HTML, code, manifests, and links pointing to old casing are not edited.
When to use it
- Standardize a small set of web-asset names.
- Normalize uppercase extensions.
- Create lowercase copies for a case-sensitive deployment workflow.
When not to use it
- Do not process case-colliding names without review.
- Do not expect locale-specific controls.
- Do not assume links or imports update automatically.
Worked examples
Asset
- Input
HeroImage.PNG- Expected output
heroimage.png
Every cased character is transformed.
Collision pair
- Input
A.txt and a.txt- Expected output
Duplicate-name risk
No disambiguation occurs.
Already lowercase
- Input
notes.md- Expected output
notes.md
The name remains the same.
Common mistakes
Forgetting references
Case-sensitive links may break. Correction: Update dependents with a mapping.
Ignoring collisions
Names can collapse. Correction: Review the batch first.
Expecting disk rename
The page creates ZIP copies. Correction: Extract and replace deliberately.
Best practices
- Check for case-insensitive duplicates.
- Update dependent references together.
- Keep originals until the destination is verified.
Related operations and differences
Add Prefix to Filenames
Choose Add Prefix to Filenames when you need to add a prefix to selected filenames.; use Lowercase Filenames specifically for rename lower.
Add Suffix to Filenames
Choose Add Suffix to Filenames when you need to add a suffix before every extension.; use Lowercase Filenames specifically for rename lower.
Replace Text in Filenames
Choose Replace Text in Filenames when you need to replace exact text across selected filenames.; use Lowercase Filenames specifically for rename lower.
Uppercase Filenames
Choose Uppercase Filenames when you need to convert selected filenames to uppercase.; use Lowercase Filenames specifically for rename lower.
Compare Two Files
Choose Compare Two Files when you need to compare two files securely by SHA-256.; use Lowercase Filenames specifically for rename lower.
File Checksum Comparator
Choose File Checksum Comparator when you need to compare a file digest with an expected checksum.; use Lowercase Filenames specifically for rename lower.
Limitations and privacy
- No locale selector, transliteration, preview, mapping, collision handling, path preservation, reference updating, or in-place rename.
- Extension is also changed.
- Output is renamed-files.zip.
Processing happens in this browser. Selected file contents are not uploaded by this tool.
Downloads and copied results remain on this device; handle them according to their sensitivity.
Frequently asked questions
Does it lowercase extensions?
Yes.
Can collisions occur?
Yes.
Does it update links?
No.
Are original files modified?
No.