Free online tool

Slowed Reverb for iPhone

Make slowed + reverb edits on iPhone in Safari. Pick a song from the Files app, set speed, reverb and bass, save the MP3 to Files. Free, no app, no upload.

Open the free editor: upload MP3, WAV, AAC, OGG or FLAC, adjust speed, reverb, bass, tone, width and space, then export MP3 or a ZIP of many tracks. Everything runs in your browser.

Making a slowed reverb edit on an iPhone works in Safari without an app. The editor above decodes your song on the phone, runs it through speed, reverb, bass, tone and width controls, and encodes an MP3 on the phone. Nothing is uploaded, there is no App Store download and no account. This page is about the iOS specifics: getting a file in from the Files app, where Safari puts the download, and how Safari handles Preserve pitch.

If you want the full explanation of each control, the slowed reverb maker page has it. The app page compares this editor against the subscription apps in the App Store. Android users should go to the Android page, because the file handling is different there.

One limit to state up front: there is no Safari extension for slowing YouTube on iPhone. The Slow & Reverb for YouTube extension is a desktop Chrome extension only. On iOS, the way to get the sound is this editor plus an audio file you own.

Getting a song into the editor on iPhone

Tap the editor's file area. Safari shows a sheet with options that usually include Photo Library, Take Photo or Video and Choose File. Tap Choose File. That opens the Files app browser in place.

From there you can reach:

• On My iPhone, including the Downloads folder where Safari saves things.
• iCloud Drive, if you use it. Files stored only in iCloud are fetched to the phone first, then handed to Safari, so processing still happens locally.
• Third-party locations such as Google Drive or Dropbox, when their apps are installed and enabled as Files providers.
• Recents, which is often the quickest route to something you just saved.

Tap a file to load it. To load several for a batch, tap Select in the top right of the Files browser, pick multiple files, then tap Open. The editor accepts MP3, WAV, AAC and M4A, OGG and FLAC, or anything else Safari can decode. Apple Music downloads are protected and will not decode; see the AAC page for the detail on which .m4a files work.

A song that lives in the Music app's library is not visible to the Files picker. If you own the file, export it from a computer to Files or iCloud Drive first.

Where the export lands

Tap download in the editor. Safari shows a download arrow in the address bar, and the file yourfile-remix.mp3 is saved to your Downloads location. By default that is the Downloads folder in iCloud Drive. You can change it to On My iPhone in Settings, Apps, Safari, Downloads (older iOS versions show Settings, Safari, Downloads).

To find the file, tap the download arrow in Safari and then the magnifying glass next to the file, or open the Files app and go to Downloads. From Files you can share it to a video editor, AirDrop it to a Mac, or save it to another folder.

A batch export arrives as all-remixes.zip or selected-remixes.zip. The Files app opens ZIPs natively: tap the ZIP and it extracts a folder next to it containing one MP3 per track.

Preserve pitch in Safari

With Preserve pitch off, slowing a song also lowers its key, which is the classic slowed sound. With it on, the editor asks the browser to time-stretch the audio so the tempo changes and the key stays put.

The quality of that time-stretch is up to the browser, and Safari's implementation sounds different from Chrome's. At moderate settings, say 0.85x to 1.25x, the difference is small. Toward the extremes of the range, Safari may show more warble on sustained notes or a slight smearing of transients. With Preserve pitch off, the export uses the same chain as the preview, so what you hear while playing is what you will get in the file. Preserve pitch changes the live preview only; exported files keep the speed-linked pitch, so an in-key file has to be made in Audacity or a DAW. Listen before you export, and if the pitch-preserved result sounds off at 0.70x, try 0.78x instead. The preserve pitch page goes into what the switch does and where it struggles.

For the classic slowed + reverb style, leave Preserve pitch off. The pitch drop is part of the sound, and Safari handles plain playback-rate changes cleanly.

Processing time and keeping Safari awake

iPhones are fast, but Safari is strict about tabs that leave the foreground. If you switch apps or the screen locks while a render is running, iOS may suspend the tab and the job stalls until you return. Keep Safari open and the screen awake until the download arrow shows the file is complete. For a batch, set Auto-Lock to a longer interval in Settings, Display and Brightness, or just keep tapping the screen.

A single song renders in a short wait on a recent iPhone. An album batch is a sit-with-it job on any phone. The processing chain is the same code as on desktop, so the result is identical; only the time differs. If you have a Mac or PC available, batches are more comfortable there, and the bulk converter page explains why batch size matters for memory.

Settings that translate to iPhone speakers

Because you are on the device most of your listeners will use, check every edit on the iPhone speaker before posting. Bass that feels huge on AirPods can disappear on the speaker, and stereo width above 1.2 can thin the sound when the phone sums it toward mono.

Save the one you settle on with Create preset. Presets are stored in Safari's local storage on this iPhone and persist between visits. They do not sync to your Mac or iPad, because there is no account.

Add to Home Screen

Open slowandreverb.com in Safari, tap the Share button (the square with an upward arrow at the bottom of the screen), scroll down and tap Add to Home Screen, then tap Add. You get an icon that opens the editor full screen without the Safari toolbar. It is the same website, so nothing extra to update. Saved presets carry over, because the home screen version uses the same storage.

Export format, stated plainly

Every export is MP3 at 96 kbps, 32 kHz, encoded in a web worker. There is no WAV, AIFF or ALAC output, and no higher bitrate option. For TikTok, Instagram Reels, YouTube and Shorts that is fine, because each of those services re-encodes your upload. If you need a lossless master, process a WAV source on a computer in a DAW.

Other browsers on iOS

Chrome, Firefox and Edge on iPhone all use Safari's WebKit engine underneath, so they behave the same as Safari for decoding, time-stretch quality and downloads. The file picker and download location may be presented slightly differently, but the editor itself is identical. Extensions for those browsers on iOS are not available.