CONVERT AVI → MP4 (AVI to MP4)
Convert legacy AVI video to modern, efficient MP4 format.
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HOW TO CONVERT AVI → MP4
Upload the AVI
Drop your .avi file. We probe the codec and audio track to pick the optimal conversion path.
Convert to H.264 MP4
FFmpeg re-encodes with H.264 video and AAC audio using CRF-based quality control.
Download the MP4
Get a web-ready MP4 that plays everywhere — no codec packs, no VLC, no warnings.
Converting AVI to MP4 re-muxes or re-encodes a legacy Microsoft container into the modern H.264/AAC MP4 that every browser, phone, and streaming service plays natively. Our converter auto-detects the AVI codec — whether DivX, Xvid, MJPEG, or uncompressed — and produces an MP4 that streams inline on Twitter, Instagram, YouTube, iOS, and Android without the codec-missing errors that AVI routinely triggers.
Why convert AVI to MP4
AVI is a 1992-era container that modern players support only reluctantly. Mobile browsers, HTML5 video, Apple devices, and every social platform expect MP4. Converting once gives you universal compatibility, hardware-accelerated decoding, and the ability to share clips without asking recipients to install VLC.
AVI vs MP4 — Technical specifications
Side-by-side comparison of the technical details.
AVI
- MIME type
- video/x-msvideo
- Extension
- .avi
- Container
- RIFF
- Max file size
- 2 GB (original); 4 GB (OpenDML extension)
- Codec support
- Any codec via FourCC identifiers
- MIME Type
- video/x-msvideo
- Category
- Video Files
- Full Name
- AVI Video
- Conversion Engine
- FFMPEG
MP4
- MIME type
- video/mp4
- Extension
- .mp4
- Container
- ISO Base Media File Format (ISO/IEC 14496-12)
- Max file size
- Practically ~16 TB; 2^63 bytes theoretical
- MIME Type
- video/mp4
- Category
- Video Files
- Full Name
- MP4 Video
- Conversion Engine
- FFMPEG
- Common video codecs
- H.264 (AVC), H.265 (HEVC), AV1, VP9
- Common audio codecs
- AAC, MP3, FLAC, Opus
- Streaming
- Supported with faststart (moov atom at front)
| Specification | AVI | MP4 |
|---|---|---|
| MIME type | video/x-msvideo | video/mp4 |
| Extension | .avi | .mp4 |
| Container | RIFF | ISO Base Media File Format (ISO/IEC 14496-12) |
| Max file size | 2 GB (original); 4 GB (OpenDML extension) | Practically ~16 TB; 2^63 bytes theoretical |
| Codec support | Any codec via FourCC identifiers | — |
| MIME Type | video/x-msvideo | video/mp4 |
| Category | Video Files | Video Files |
| Full Name | AVI Video | MP4 Video |
| Conversion Engine | FFMPEG | FFMPEG |
| Common video codecs | — | H.264 (AVC), H.265 (HEVC), AV1, VP9 |
| Common audio codecs | — | AAC, MP3, FLAC, Opus |
| Streaming | — | Supported with faststart (moov atom at front) |
AVI vs MP4 — Strengths and limitations
What each format does best, and where it falls short.
AVI Strengths
- Simple, well-documented format — trivial for any video library to parse.
- Universal Windows playback since Video for Windows in 1992.
- Low encoding overhead — interleaved structure is fast to write.
- Works with any codec technically, including modern ones.
Limitations
- Aging container — no native support for chapters, subtitles, or multi-audio selection.
- File-size limits (2 GB original, 4 GB with OpenDML) break for HD content.
- Variable-framerate video causes sync drift.
MP4 Strengths
- Universal playback — every browser, phone, TV, game console, and editing suite reads MP4.
- Supports modern codecs (H.264, H.265, AV1) with no container changes.
- Progressive streaming works with the "moov atom" at the start of the file.
- Carries subtitles, chapters, multiple audio tracks, and embedded metadata.
- ISO-standardized (ISO/IEC 14496-14) and patent-licensable via MPEG LA.
Limitations
- Codec licensing (H.264, H.265) carries royalty costs for commercial use.
- Streaming requires the moov atom at the start — a misplaced atom breaks web playback.
- Not ideal for lossless or professional editing workflows (use ProRes or DNxHD instead).
Quality & Compatibility
H.264 is a modern lossy codec tuned for perceptual quality; CRF 20–23 produces a file visually indistinguishable from the AVI source while typically halving size. Audio is re-encoded to 192 kbps AAC by default.
Tips for Best Results
- DivX and Xvid AVI files transcode quickly — FFmpeg can often stream-copy the video and only re-encode audio.
- If playback looks jerky, check that the AVI has a constant frame rate; variable-FPS AVIs need extra processing.
- For archival quality, use CRF 18; for social uploads, CRF 23 halves the size with no perceptible loss.
Frequently Asked Questions
Only when it has to. If the codecs inside AVI (usually H.264 or H.265 for video, AAC for audio) are accepted by MP4, we stream-copy — the bytes are repackaged into the new container with zero re-encoding and no quality loss. When the source uses a codec the target does not support, we transcode at a matching bitrate to keep the visual quality close to the original.
Slight loss, since H.264 is lossy. At CRF 20–23 the difference from the source is imperceptible on normal viewing. For pure archival, use CRF 18 or keep the AVI original alongside.
With stream copy, expect the job to finish in seconds to tens of seconds regardless of video length — the work is mostly rewriting the container. Transcoding is slower (roughly real-time: a ten-minute clip takes about ten minutes) because every frame must be decoded and re-encoded. The progress bar shows which mode applies.
AVI uses old codecs (DivX, Xvid, MJPEG) that modern phones do not decode natively. MP4 with H.264 is the universal mobile-friendly format.
Yes. Resolution, frame rate, colour space and bit depth are preserved by default; stream copy is literally bit-identical on these parameters. If you explicitly pick a lower bitrate or a different codec in Advanced, the output is rebuilt to those settings, but the default is always "match the source".
Embedded subtitle tracks are copied where possible; external .srt files stay external. Hard-coded (burned-in) subtitles are part of the video and always preserved.
If the AVI already uses H.264 (rare but possible), we stream-copy the video and only repackage the container — seconds rather than minutes.
AVI Video
Source formatAVI is a legacy Microsoft multimedia container that stores audio and video data. While largely superseded by modern formats, it remains widely recognized and is produced by many older devices and screen recorders.
MP4 Video
Target formatMP4 is the most universally supported video container format. It typically uses H.264 or H.265 video codecs with AAC audio, providing an excellent balance of quality and file size across all devices and platforms.
Going the other way? Convert MP4 back to AVI with the same engine.
Common Use Cases
Archive old camcorder footage
MiniDV captures are often AVI — convert to MP4 for cloud backup and modern playback.
Social media uploads
Twitter, Instagram, and TikTok all reject AVI; MP4 uploads without transcoding.
iPhone and iPad playback
iOS refuses AVI natively; MP4 plays in Photos, Safari, and AirDrop without third-party apps.
Web embeds
HTML5 <video> expects MP4; AVI requires clunky object-tag fallbacks.
AVI vs MP4 — Typical file sizes
Approximate file sizes for common scenarios.
- 10-min video (XviD / MP3) 100-200 MB
- 45-min TV episode (DivX) 350-700 MB
- 2-hour movie (DVD rip) 700 MB - 1.4 GB
- Smartphone video (1080p, 1 min) 60–120 MB
- 4K video (1 min, H.265) 200–400 MB
- Streamed movie (90 min, H.264) 1–4 GB
Working with 4K/8K Video or Files Over 100MB?
Web browsers impose strict RAM limits on media streams. For gigabyte 4K/8K footage, GPU-accelerated NVENC transcode, or batch subtitle muxing, dedicated desktop encoders deliver zero upload delays.
One-time payment with zero recurring commitment: convert files up to 1 GB, OCR, PDF/A, and .ZIP batches for 24 hours.
Full 7 days of unlimited conversions, up to 2 GB per file, 100% ad-free with zero subscription.
High-throughput enterprise pipeline for files up to 2,048 MB, 50-file batches, ISO PDF/A, and priority processing.
Uncapped 4K/8K multi-track transcoding with hardware NVENC, VideoToolbox, and AV1/HEVC pipelines.
10-bit color grading workflows, Apple ProRes mastering, and automated watch-folder queues.
Related comparisons
See these formats side by side to understand which fits your use case best.
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