A free online audio file renamer, silence trimmer and normalizer
Audio Files Prep is a free online tool for anyone who manages a library of sound files: radio producers, podcasters, video editors, game developers, sound designers and soundboard users. It brings together three jobs that usually need three different programs: renaming audio files, trimming the silence at the start and normalizing the volume. It works on MP3, WAV and AIFF files, one at a time or in batch, directly in your browser.
Rename MP3 and WAV files online, fast
Most file renamers only show you a name. When you are sorting sound effects, jingles or voice clips, the name rarely tells you what is inside, so you end up opening every file in a player. Here, each file plays as soon as you select it: you listen, type a clear name and press Enter. The file is renamed on your disk and the next one starts. A category prefix such as SFX_, JINGLE_ or MUSIC_ stays active from one file to the next, so a consistent naming convention takes no extra effort.
For renaming in bulk, tick any number of files and use the batch tools. You can remove a prefix (SFX_whoosh becomes Whoosh), find and replace characters (for example, replace every underscore with a space), or switch the whole selection to ALL CAPS, Capitalize Each Word or lowercase. A before/after preview shows every change before it is applied, and a file is never overwritten. If two files would end up with the same name, that change is skipped.
Remove silence from the beginning of audio files
Leading silence is the classic problem with sound libraries: you press play and nothing happens for half a second. Audio Files Prep detects where the sound really starts using a threshold you choose (−40 dBFS by default), keeps a short pre-roll so attacks are never clipped, and adds a few milliseconds of fade-in to avoid a click. The red area on the waveform shows exactly what will be cut. On WAV and AIFF files, the trim is completely lossless: the original samples are copied as they are, with the same sample rate, bit depth and metadata.
Normalize audio volume to the same loudness (LUFS)
Peak normalization makes the loudest sample hit the same level, but two files normalized that way can still sound very different. Audio Files Prep normalizes perceived loudness instead, measured in LUFS according to ITU-R BS.1770 and EBU R128, the standards used in broadcasting and on streaming platforms. Pick a target such as −16 LUFS, set a true-peak ceiling (−1 dBTP by default) and a look-ahead limiter catches any peak that would go over, including inter-sample peaks. The result: every file plays at the same volume without clipping. Files that need heavy limiting or very high gain are flagged so you can check them by ear first.
Create a loop of any length
Have a 20-second music bed but need three minutes under a segment? The loop creator repeats a seamless loop as many times as you want, or until it reaches a target duration, and adds an optional fade-out at the end. The result is saved as a new file next to the original, for example Morning_Bed_loop_3m00.wav. On WAV and AIFF the loop is copied sample for sample, so a well-cut loop stays perfectly seamless. Silence at the start or end of the loop is detected and removed, with cut points snapped to the nearest zero crossing to avoid clicks. You can also set the loop start and end yourself, by dragging two handles on the waveform or typing values to a tenth of a millisecond, with a zoomed view of the junction to check that the waveform joins smoothly. Then listen to the loop point (the last two seconds followed by the first two) before creating the file, and anything suspicious, such as a click at the junction or an MP3 without gapless information, is flagged.
Private by design: your files are never uploaded
Online audio tools usually make you upload your files, wait, then download them again. Audio Files Prep doesn’t. Everything runs locally in your browser, and changes are written straight back to your files using the File System Access API built into Chrome and Edge. Nothing is sent to a server, which also makes it fast: renaming a hundred files takes seconds, not minutes of uploading. An optional backup keeps a copy of every original before audio processing.
Supported formats and requirements
- WAV (16, 24 and 32-bit integer or float) and AIFF: renaming, lossless trimming, lossless loop extension and loudness normalization, in the original format.
- MP3: renaming, trimming, normalization and loop extension. Processed MP3 files are re-encoded at 320 kbps with gapless information and the original ID3 tags.
- M4A, AAC, FLAC, OGG, Opus: renaming and analysis only.
- A desktop version of Google Chrome or Microsoft Edge. Safari, Firefox and mobile browsers can’t yet give a website access to a folder.