All tools
Random strings
Add random characters to file names
Random characters are useful when files need lightweight unique IDs but do not need meaningful sequence numbers. Renamio previews the generated names before you apply them.
Best for
Use this when many files need short unique suffixes, upload-safe names, or randomized IDs.
Rename examples
Random suffix
document.pdf
document_A7B9.pdf
Random prefix
image.png
R4K2_image.png
Numeric ID
export.csv
export_839201.csv
Common use cases
- Reduce name collisions before uploads or exports.
- Add short tracking IDs to generated files.
- Create randomized file names for samples or temporary batches.
How to use it
- 1Choose the random fill rule.
- 2Pick character types and length.
- 3Preview the generated names, then apply the rename.
Limits and checks
- Use random strings when uniqueness matters more than human-readable names.
- Choose a length that is long enough for the batch size.
- Keep a stable prefix or date if files still need to be grouped later.
Common mistakes to avoid
- Using very short random strings in large folders.
- Replacing the whole name with random text when the original context is still useful.
- Skipping preview because random output still needs collision checks.
FAQ
Can I choose letters and numbers separately?
Yes. You can choose numbers, lowercase letters, uppercase letters, Chinese numbers, or a custom character set.
Will the random value change in preview?
Rules that generate random output can be reapplied so you can regenerate the preview when needed.