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appkiro.comMerge audio files
Runs in your browserNo upload · No watermark · Free
Merge Audio combines multiple audio files into a single track. Drag to reorder, preview each file with one click, blend transitions with a crossfade of up to 3 seconds, and export to MP3, WAV, FLAC, OGG (Vorbis), Opus, AAC, or M4A. Decoding, mixing, and encoding all run locally with the browser's WebCodecs API — files never reach a server.
1. Add Audio Files
Up to 30 tracks. 2 GB per file.
Drag & drop audio files here
or
Supported: MP3, WAV, M4A, AAC, OGG, FLAC
What this tool does
Stitch several audio recordings into a single file. Use it to assemble a podcast from intro/main/outro segments, glue voice memos together, build a class compilation, or join multiple stems for delivery. Every step happens inside your browser — no upload, no queue, no watermark.
How to use Merge Audio
- 1
Add audio files
Drag and drop one or many files onto the dropzone, or click Choose files to pick them. You can mix MP3, WAV, M4A, AAC, OGG, and FLAC freely — the tool reads each file and shows a waveform plus duration.
Add step — dropzone with supported formats and Choose files button - 2
Arrange the order
Drag the grip handle on the left to reorder rows, or use the row menu's Move up / Move down. Click the play icon on a row to preview it standalone, or hit Play all to audition the sequence one file after another.
Arrange step — track list with waveforms, drag handles, play controls - 3
Pick a crossfade
Use the Crossfade dropdown in the section header to set the overlap between consecutive tracks. Off produces hard cuts; 0.5 to 3 seconds applies an equal-power fade-out / fade-in for smooth transitions.
- 4
Choose output format and quality
Open the Output format dropdown to compare codecs and pick MP3, WAV, FLAC, OGG, Opus, AAC, or M4A. Greyed-out entries are not encodable in your browser. For lossy formats, set the bitrate (96 to 320 kbps); lossless WAV/FLAC ignore the bitrate setting.
Format step — Output format and quality selectors with merge button - 5
Merge and download
Click Merge to <format>. A progress bar reports decoder/encoder progress; cancel any time. When it finishes, a download button appears with the size and total duration of the merged file.
Merge step — progress bar then download button with stats
Output format guide
| Format | Type | Best for | Notes |
|---|---|---|---|
| MP3 | Lossy | Universal compatibility | Plays everywhere; encoder may not be present in every browser. |
| WAV | Lossless | Editing, archival masters | Uncompressed PCM; large files. |
| FLAC | Lossless | Smaller lossless masters | ~50% the size of WAV with identical audio. |
| OGG (Vorbis) | Lossy | Open-source toolchains, games | Royalty-free, broad Linux support. |
| Opus | Lossy | Voice, low-bitrate streaming | Best perceived quality at 64–128 kbps. |
| AAC (ADTS) | Lossy | Streaming pipelines, HLS | Raw AAC frames in an .aac container. |
| M4A (AAC in MP4) | Lossy | Apple devices, iTunes/Music | AAC packaged in MP4 — best Apple ecosystem support. |
Tips
- Match your sources — if all tracks are stereo at 44.1 kHz, the merge is fastest. Mixed sample rates auto-resample.
- For seamless music compilations, set crossfade to 2 or 3 seconds.
- For spoken-word podcasts, use 0.5 sec or Off to keep timing tight.
- Reorder by dragging — keyboard users can use the row menu's Move up / Move down items.
- Pick FLAC if you plan to re-edit the merged file later. Pick MP3 or M4A for distribution.
Frequently asked questions
Are my audio files uploaded to a server?
No. Decoding, mixing, crossfading, and encoding all run inside your browser using the WebCodecs API. Files never leave your device.
Which formats can I merge?
MP3, WAV, M4A, AAC, OGG (Vorbis/Opus), FLAC — any audio file your browser can decode. Files with different sample rates and channel counts are auto-resampled to a common target.
Which output formats can I export?
MP3, WAV, FLAC, OGG (Vorbis), Opus, AAC (ADTS), and M4A. Codecs your browser cannot encode are greyed out in the format dropdown.
What does Crossfade do?
Crossfade overlaps the tail of one track with the head of the next: the outgoing track fades out while the incoming track fades in. Pick 0 for hard cuts or 0.5–3 seconds for smooth transitions.
Can I reorder tracks?
Yes. Drag the grip handle on the left of each row to reorder, or use Move up / Move down in the row menu.
Why is one of the formats greyed out?
Your browser cannot encode that codec. MP3 encoding in particular is not native in every browser. Use Chrome or Edge for the broadest coverage, or pick another format.
What is the maximum size?
2 GB per file, up to 30 tracks per merge. Decoding streams samples through memory rather than buffering the whole file.
Will the merged file be louder than the originals?
Crossfade overlaps fade in and fade out cleanly with equal-power ramps, so the perceived loudness stays even. No automatic normalization is applied.