k2
Don’t want to install k2? Drop the file here.
The first 20 minutes of any recording are transcribed free: a recording up to 20 minutes transcribes in full, a longer one is previewed, and a pack from $6 (500 minutes) transcribes the rest and opens every export, and credits never expire.
FSA/FST framework written from scratch in PyTorch/CUDA.
Best for differentiable WFST / lattice training on modern GPUs. Pricing: free.
What it is
k2 is the FSA/FST engine that powers icefall and sherpa. Brings Kaldi-style decoders to PyTorch with autograd. Apache-2.0.
Watch out for: Niche audience; requires deep familiarity with FSA decoding.
Install / use
pip install k2What people actually do with k2-style transcription
The tool is the means. These are the jobs — each one priced at published rates, each one wired up on its own page.
Features
| Speaker diarization | No |
| Word-level timestamps | Yes |
| Streaming / real-time | No |
| Languages supported | 40 |
| HIPAA eligible | No |
Links
k2 vs Whipscribe
| Feature | k2 | Whipscribe |
|---|---|---|
| Category | Open source | Transcription APIs |
| Pricing | free | $6–$24 one-time packs (credits never expire) · first 20 minutes free |
| Speaker identification | No | Named in the summary, key quotes and chapters |
| Word timestamps | Yes | Yes |
| Streaming | No | No |
| Languages | 40 | 99 |
| Platforms | Linux | Web, API, MCP |
Alternatives to k2
Frequently asked about k2
Is k2 free?
Yes. k2 is free and open source.
Does k2 work on Mac, Windows and Linux?
k2 runs on Linux. It is not listed for other platforms; check the vendor for anything beyond Linux.
How do I install k2?
With pip: `pip install k2`. You need Python and, for most audio tools, ffmpeg on your PATH first.
How many languages does k2 support?
k2 lists 40 languages.
Does k2 identify different speakers?
No. k2 does not label speakers; a conversation comes back as one continuous text. If you need speaker labels, that is a separate tool or a different service.
Does k2 give word-level timestamps?
Yes — k2 produces timing per word, which is what subtitle cues and clip boundaries need.
Can k2 transcribe live audio?
No — k2 works on finished files, not a live stream.
Is k2 HIPAA compliant?
k2 does not claim HIPAA compliance. For PHI, run it on infrastructure you control or choose a service that will sign a BAA.
What are the limitations of k2?
Niche audience; requires deep familiarity with FSA decoding.
Who is k2 best for?
Differentiable WFST / lattice training on modern GPUs.
Does k2 run offline?
k2 runs on your own machine — it is open source, so nothing leaves the computer unless you configure it to.
Can I use k2 in the browser?
No — k2 is a Linux application, not a web app. You install it rather than sign in to it.
Where is the k2 source code?
On GitHub at github.com/k2-fsa/k2. It is maintained by k2-fsa.
What kind of tool is k2?
In this directory k2 is filed under toolkit, framework, decoder as a open-source tool.
What are the alternatives to k2?
There is a side-by-side page at /tools/k2-alternatives comparing k2 with the closest tools in the same category on price, platform and features.
Whipscribe is a hosted transcription service. If you want transcripts without running infrastructure, paste a URL or drop a file in the form below — you'll have a transcript in seconds.
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