Add Prefix to Filenames
Add Prefix to Filenames places the entered value directly before each full filename, including its basename and extension, then packages the copies in renamed-files.zip. An empty field falls back to prefix-. The page performs no separator insertion beyond what you enter, collision prevention, character validation, path handling, or in-place filesystem rename.
Runs locally — files stay on your deviceWhere is the prefix inserted?
Immediately before the complete original filename.
A prefix becomes the first filename characters
Unlike a suffix-before-extension operation, prefixing does not need to split the basename from the extension.
How it works
For each selected file, the prefix or prefix- fallback is concatenated with its name; JSZip writes the copies to renamed-files.zip.
Key concepts
Literal concatenation
Add your own dash, space, or underscore when wanted.
Empty has a fallback
Leaving the field blank adds prefix-.
When to use it
- Add a project code to a batch.
- Mark exported copies with a date you supply.
- Group flat filenames by a common leading token.
When not to use it
- Do not expect originals to change.
- Do not use unchecked characters for a destination filesystem.
- Do not assume duplicates will be resolved.
Worked examples
Project code
- Input
Prefix PRJ-; report.pdf- Expected output
PRJ-report.pdf
The prefix is inserted literally.
No separator
- Input
Prefix 2026; photo.jpg- Expected output
2026photo.jpg
No punctuation is added automatically.
Blank value
- Input
notes.txt- Expected output
prefix-notes.txt
The fallback is used.
Common mistakes
Omitting a desired separator
Concatenation is literal. Correction: Include - or _ in the prefix.
Expecting in-place changes
The output is a ZIP. Correction: Extract the new copies.
Creating collisions
Output uniqueness is unchecked. Correction: Review the batch.
Best practices
- Use short portable prefixes.
- Preview expected names mentally or with a small batch.
- Keep originals until downstream links are updated.
Related operations and differences
Add Suffix to Filenames
Choose Add Suffix to Filenames when you need to add a suffix before every extension.; use Add Prefix to Filenames specifically for rename prefix.
Lowercase Filenames
Choose Lowercase Filenames when you need to convert selected filenames to lowercase.; use Add Prefix to Filenames specifically for rename prefix.
Replace Text in Filenames
Choose Replace Text in Filenames when you need to replace exact text across selected filenames.; use Add Prefix to Filenames specifically for rename prefix.
Uppercase Filenames
Choose Uppercase Filenames when you need to convert selected filenames to uppercase.; use Add Prefix to Filenames specifically for rename prefix.
Compare Two Files
Choose Compare Two Files when you need to compare two files securely by SHA-256.; use Add Prefix to Filenames specifically for rename prefix.
File Checksum Comparator
Choose File Checksum Comparator when you need to compare a file digest with an expected checksum.; use Add Prefix to Filenames specifically for rename prefix.
Limitations and privacy
- No preview, validation, collision handling, paths, metadata guarantees, or in-place rename.
- Empty input uses prefix-.
- The entire batch is downloaded as 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
Is a dash added automatically?
Only the fallback includes one; otherwise enter it yourself.
Is the extension preserved?
Yes, because the prefix is added before the full original name.
Are originals modified?
No.
Can I use spaces?
The text is used literally, subject to destination compatibility.