Batch File Renamer
Create a reviewable rename plan for a selected group of files, then download copies under the accepted names in a new ZIP. Your original files stay untouched. Each input has its own row identity, so two files with the same name remain separate throughout the plan and export.
Key features
- Apply a fixed or original stem, literal replacement, casing, prefixes, suffixes and numbered sequences in a declared order.
- Keep, lowercase, uppercase, replace or remove the last filename extension; file contents are not converted.
- Choose selection order or deterministic name order, with explicit up/down controls for the selection list.
- Review exact-name collisions or optional NFC-plus-lowercase collisions, conservative reserved names and length limits.
- Block a conflicting batch or append reviewed numeric suffixes without overwriting another planned name.
- Export original file bytes in a new STORE ZIP, plus CSV and JSON mappings; cancel reading/packing and discard stale results.
How to use
- Choose up to 100 files or load the clearly labeled synthetic example. Review the displayed order and sizes.
- Choose name, extension and sequence rules. Selection order uses the displayed list; name order uses UTF-16 string comparison with stable ties.
- Create the plan. Inspect every proposed/output name and resolve blocked rows before making a ZIP.
- Download CSV or JSON for review, or make the accepted ZIP. Cancel with the button or Escape while working.
- Download renamed-files.zip. Its files/ entries contain the original bytes, and its root contains both rename reports.
Use cases
- Number lesson handouts in a chosen order while preserving their PDF and image bytes.
- Give a batch of scans one base name and a padded sequence before sharing a new bundle.
- Inspect case-sensitive versus NFC-plus-lowercase name collisions before choosing output names.
- Make a traceable archive containing both the renamed copies and their original-to-new mapping.
Frequently asked questions
Does this rename the files on my device?
No. The tool reads selected files only when you request the ZIP and places their unchanged content bytes under new entry names. It does not write to the original folder or request disk-write access. Extract the downloaded archive into a location you choose.
How are numbering and extensions handled?
Numbering follows either the displayed selection list or ascending UTF-16 name order; equal names retain their list order. You can move selected rows up or down. Only the last non-leading, non-trailing dot defines an extension: archive.tar.gz has stem archive.tar, while .env has no extension. Changing an extension does not convert a format.
What is the default collision policy?
The default is exact, case-sensitive string equality with no Unicode normalization, and collisions block the whole ZIP. The optional comparison normalizes names to NFC, lowercases them, then normalizes again for comparison only. Output spelling is preserved. This is not full Unicode case folding or an exact emulation of every filesystem.
Which names are rejected and can automatic suffixes fix everything?
The conservative output policy rejects path separators, control characters, Windows-style forbidden characters and device names, trailing dots/spaces, malformed surrogate characters and names exceeding either 255 UTF-16 units or 255 UTF-8 bytes. Automatic suffixes address duplicate proposals only; all other blocked names must be corrected. Generated suffixes reserve every original proposal so another row is not overwritten. Destination path limits and extraction-app behavior can still differ.
What is preserved in the ZIP and reports?
Every accepted file keeps its content bytes, including binary and empty files. The archive uses STORE compression and a fixed 2000-01-01 timestamp; original permissions, timestamps and other filesystem metadata are not preserved. CSV cells that could begin spreadsheet formulas receive a leading apostrophe, while JSON and ZIP filenames keep their exact declared names.
What are the limits and what happens on cancellation?
Select 1–100 files, at most 16 MiB each and 32 MiB in total; the ZIP is capped at 40 MiB. Name rules are bounded and a replacement expanding a stem past 4,096 units is rejected before allocation. Files are read sequentially, and packing yields between chunks. Cancellation pauses the ZIP stream and discards output; an already pending native file read may finish internally, but its late result is ignored. Changing inputs or rules invalidates the old plan and download.
Privacy
Selected file metadata, rename rules and file bytes stay in this page’s memory. This tool does not upload them or save them to browser storage. Planning reads metadata only; making the ZIP reads the selected contents. Clearing, replacing inputs or leaving the page releases the tool’s references and download URLs. The synthetic example uses real in-memory File objects and does not demonstrate native file-picker permission.
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