Sync vs. Async Transcription: Which to Use (2026)

Short summary

AssemblyAI explains when to use sync versus async transcription for recorded audio. Async submits a job and returns results via polling or webhook, handling any file length at $0.21/hr with diarization and deep speech understanding. Sync returns a transcript in the same HTTP response at ~134ms p50 for clips up to 2 minutes at $0.45/hr, trading file-length scope and advanced features for speed. Both paths deliver identical accuracy — the choice is about latency tolerance and feature needs.

• •Async: any file length, $0.21/hr, includes diarization and speech understanding, results in seconds-to-minutes
• •Sync: clips up to 2 min, $0.45/hr, ~134ms p50, no diarization or PII redaction
• •Sync returns transcripts faster than real time — an 8-second clip transcribes in under a second

Generated with AI, which can make mistakes.