Does renaming change the audio inside the file?

No. The file you save is byte for byte the file you dropped, because the download is an object URL of the original rather than a copy the tool produced. That means the encoding, the tags and the bit rate all survive intact, and renaming cannot introduce a generation loss the way a re-encode would.

How does the numbering work?

Each file takes the next number in the order it was dropped, starting from your start value and padded to the width you choose. A width of three turns one into a three character string with two leading zeros, which matters for sorting: without padding, a list will order the tenth file ahead of the second.

What happens to characters the file system rejects?

They are replaced with a character you choose, which defaults to a hyphen. That covers the punctuation and reserved symbols that cannot appear in a file name on common systems, so a plan that is valid in the browser produces a name that is also valid when saved. The result is trimmed before the extension is appended.

Why do the files download one at a time?

Because each row has its own save control and the tool hands over the original file object rather than bundling an archive. That keeps the operation simple and guarantees the bytes are untouched, at the cost of a separate download for every file in a long batch.

Can I reorder the files before numbering?

Not directly, since numbering follows the order in which the files were dropped. To control the sequence, drop them in the order you want, or add a step to your own workflow first. Sorting a batch after the fact would break the link between the plan shown and the files saved.

Batch File Renamer

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Audio Format Converter

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Batch File Renamer plans and applies new names for a group of audio files dropped onto it, using prefix, suffix, find and replace, letter case and numbering. Audio content is never touched: each saved file is a byte identical copy under a new name.

What is Batch File Renamer?

Drop one file or fifty and the panel builds a plan, showing every original name beside the name it will become. Each row carries its own save control, so files come back one at a time under their new names, straight from an object URL of the original file.

What the panel offers:

A prefix and a suffix, placed around the existing base name and before the extension.
Find and replace applied to the base name only, leaving the extension alone.
Letter case normalisation to lowercase or uppercase, or left exactly as it was.
Numbering with a start value from 0 to 9999 and a zero padded width from 1 to 6 digits, defaulting to three.
An option to append the total, producing names such as a sequence numbered of fifty.
Invalid character replacement, defaulting to a hyphen, for the characters that file systems will not accept.

The plan is computed in the browser from the file names alone, with no reading of file contents. Each name is split into a base and an extension against a fixed list of audio extensions, the find and replace step runs on the base, case normalisation is applied, and then the prefix, suffix and number are assembled around it. The extension is preserved from the original name rather than taken from the rebuilt base, so a file cannot lose its format along the way. Anything a file system would reject is replaced with the chosen character, and the result is trimmed before the extension is appended. Verified behaviour is that the saved file is byte for byte the file you dropped, because what is downloaded is an object URL of the original file rather than a re-encoded copy.

What the renamer does not do:

It cannot read audio content, so numbering is positional rather than derived from duration, tempo or any other property.
Files are numbered in the order they were dropped, which may not match alphabetical or chronological order.
Saving is per file rather than as an archive, so a large batch means a large number of downloads.
Replacing a character that already appears elsewhere in a name can produce collisions, which the plan shows but does not resolve.
A find and replace that matches nothing is silent, so a mistyped search term leaves the plan unchanged.
Names are changed in the browser only; the files on your disk keep their original names until each one is saved.

Use it for a batch rename at the start of a delivery, so a set of files sorts sensibly, and keep the zero padded width consistent so a sequence does not jump between two and three digits part way through. Because nothing is re-encoded, it is also the safe way to relabel an archive: the audio, its tags and its bit rate all survive exactly as they arrived. Because the plan is shown before anything is saved, the moment to catch a mistake is before you click rather than after, so read two or three rows of the plan instead of trusting the fields you typed.

How to use Batch File Renamer

Drop one or more audio files onto the panel; the plan updates for every file at once.
Fill in the prefix, suffix, find and replace fields, and choose a letter case if you want one.
Set numbering, picking a start value and a zero padded width so the sequence sorts correctly.
Check the plan rows, then save each file from its own control under the new name.

When to use Batch File Renamer vs related tools

Batch File Renamer is a naming step, so it sits at the start or the end of a delivery rather than inside an edit. ID3 Tag Editor changes the metadata inside a file while the name stays as it was, which is a different job on the same finished episode, and Podcast Chapter Marker Tool writes chapter markers into an MP3. When the files differ in format and need converting before delivery, Audio Format Converter handles that, and Show Notes Timestamp Generator covers the text side of the same release.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.