Does Grok support MP4 video files for audio transcription?

Grok's transcription API is primarily designed for audio containers. MP4 video files may be accepted if they contain an audio stream, but it is recommended to extract the audio track first (e.g. with FFmpeg: ffmpeg -i video.mp4 -vn -ar 16000 audio.wav) to ensure compatibility.

What is the maximum audio file size Grok accepts?

Grok typically enforces a per-request file size limit of around 25 MB. For longer recordings, split the audio into shorter segments (10-15 minutes) before uploading to avoid rejection errors.

Is FLAC better than MP3 for Grok transcription?

FLAC preserves the original audio quality without loss, which can improve transcription accuracy on low-volume or noisy recordings. For clear speech at 128 kbps+, the practical difference between FLAC and MP3 in transcription output is minimal.

Can I use Grok transcription with browser-recorded WEBM files?

Yes. WEBM (with Opus audio codec) is supported and is the native output of the browser MediaRecorder API, making it convenient for web-based voice recording applications without any conversion step.

Does sample rate affect Grok transcription quality?

Yes. A minimum sample rate of 16 kHz mono is recommended. Audio recorded at 8 kHz (telephony) may show reduced accuracy. Recording above 16 kHz generally does not further improve results and increases file size.

Reference Guide · April 2026

Grok xAI Supported Audio Formats for Transcription: Complete Guide

By ScribeForge · April 25, 2026 · 6 min read

ScribeForge uses the xAI Grok STT API for browser-based transcription. Upload any supported audio file and get a transcript in seconds — no API key required. Try it free →

Grok, the AI model developed by xAI, offers powerful audio transcription capabilities. Knowing which audio file formats are supported — and their technical limits — helps you avoid upload errors and get accurate transcripts every time.

Supported audio formats
File size and duration limits
Which format gives the best accuracy?
How to convert unsupported formats
Grok vs other AI transcription tools
Frequently asked questions

Which Audio Formats Does Grok (xAI) Support?

As of 2026, Grok's transcription API accepts the following audio file formats:

Format	Type	Common use case
MP3	Lossy	Podcasts, music, most recorded audio
WAV	Uncompressed	Studio recordings, high-quality speech capture
FLAC	Lossless	Archival audio, maximum accuracy
M4A / AAC	Lossy	iOS voice memos, Apple devices
OGG	Lossy	Web and game audio pipelines
WEBM	Lossy	Browser MediaRecorder output

Note: Format support may evolve as xAI updates Grok. Always verify against the official xAI documentation before production deployment.

MP3 — Most common lossy format; widely compatible and smallest file size at equivalent quality.
WAV — Uncompressed audio; best transcription accuracy for studio or high-quality recordings.
FLAC — Lossless compressed; ideal balance between file size and quality for archival audio.
M4A / AAC — Apple-native lossy format; common output from iOS devices and voice memos.
OGG — Open-source lossy format; frequently used in web and game audio pipelines.
WEBM — Browser-native container (VP8/Opus); direct output from browser MediaRecorder API.

File Size and Duration Limits

Beyond format, Grok enforces practical upload constraints:

Max file size: up to 25 MB per request.
Max duration: recordings up to ~30 minutes per file tend to perform best; longer files should be split into segments.
Sample rate: 16 kHz mono is the recommended minimum for accurate transcription; higher rates are accepted but don't always improve accuracy.
Bit depth: 16-bit PCM recommended for WAV/FLAC files.

File too large? Split with FFmpeg: ffmpeg -i long_audio.mp3 -f segment -segment_time 900 -c copy part%03d.mp3 — this splits into 15-minute segments without re-encoding.

Which Format Gives the Best Transcription Accuracy?

For production transcription pipelines, format choice impacts quality in this rough order:

WAV (PCM uncompressed) — Zero quality loss; best results on noisy or speech-heavy audio.
FLAC — Lossless compression; virtually identical accuracy to WAV with ~40-60% smaller files.
MP3 at 128 kbps+ — Minimal accuracy loss for clear speech; fine for podcasts, interviews, meetings.
M4A / AAC at 128 kbps+ — Comparable to MP3; good choice for mobile-recorded audio.
OGG / WEBM — Acceptable for web pipelines; minor quality trade-off vs lossless.

  For most use cases (meetings, interviews, podcasts), MP3 at 128 kbps or higher is sufficient. The quality difference vs WAV is negligible for clear speech in a quiet environment. Reserve WAV/FLAC for recordings with background noise or low speaking volume where every bit of quality matters.

How to Convert Audio to a Supported Format

If your file is in an unsupported format (e.g. AMR, WMA, AIFF), convert it before uploading:

FFmpeg (CLI — recommended)

bash

# Convert any format to 16 kHz mono WAV (optimal for STT)
ffmpeg -i input.wma -ar 16000 -ac 1 output.wav

# Convert to MP3 at 128 kbps
ffmpeg -i input.aiff -b:a 128k output.mp3

# Extract audio from video
ffmpeg -i video.mp4 -vn -ar 16000 -ac 1 audio.wav

Audacity (GUI)

Open the file → File → Export → choose WAV or MP3 → set sample rate to 16000 Hz in Project Rate (bottom-left).

Online tools

CloudConvert and Zamzar support most conversions without software installation — useful for one-off files where installing FFmpeg isn't practical.

Grok Audio Transcription vs Other AI Tools

Grok's format support is comparable to OpenAI Whisper (MP3, MP4, WAV, WEBM, M4A, OGG, FLAC) and Google Speech-to-Text. The key differentiators are inference speed and context window size for post-processing.

Tool	Supported formats	Max size
Grok (xAI)	MP3, WAV, FLAC, M4A, OGG, WEBM	25 MB
OpenAI Whisper	MP3, MP4, WAV, WEBM, M4A, OGG, FLAC	25 MB
Google STT	FLAC, WAV, MP3, OGG, WEBM, AMR	Varies by tier

Tools like ScribeForge abstract format handling entirely — upload any supported file and the platform routes it to the Grok STT engine automatically, with no conversion step required on your end.

Frequently Asked Questions

Does Grok support MP4 video files for audio transcription?: Grok's transcription API is primarily designed for audio containers. MP4 video files may be accepted if they contain an audio stream, but it is recommended to extract the audio track first (e.g. with FFmpeg: ffmpeg -i video.mp4 -vn -ar 16000 audio.wav) to ensure compatibility.
What is the maximum audio file size Grok accepts?: Grok typically enforces a per-request file size limit of around 25 MB. For longer recordings, split the audio into shorter segments (10-15 minutes) before uploading to avoid rejection errors.
Is FLAC better than MP3 for Grok transcription?: FLAC preserves the original audio quality without loss, which can improve transcription accuracy on low-volume or noisy recordings. For clear speech at 128 kbps+, the practical difference between FLAC and MP3 in transcription output is minimal.
Can I use Grok transcription with browser-recorded WEBM files?: Yes. WEBM (with Opus audio codec) is supported and is the native output of the browser MediaRecorder API, making it convenient for web-based voice recording applications without any conversion step.
Does sample rate affect Grok transcription quality?: Yes. A minimum sample rate of 16 kHz mono is recommended. Audio recorded at 8 kHz (telephony) may show reduced accuracy. Recording above 16 kHz generally does not further improve results and increases file size.