AmberPen vs GrammarBot Neural
GrammarBot Neural and AmberPen are both neural proofreading APIs. We ran both products over the same 754 JFLEG development sentences and 6,845 CWEB test sentences, then scored their outputs locally with the same official tools.
Benchmark results
| Metric | AmberPen | GrammarBot Neural |
|---|---|---|
| JFLEG fluency (GLEU) | 0.561 | 0.413 |
| CWEB precision | 37.35% | 40.82% |
| CWEB recall | 65.54% | 62.52% |
| CWEB ERRANT F0.5 | 40.87 | 43.86 |
The benchmarks split the decision. AmberPen leads JFLEG by 0.148 GLEU, reflecting stronger fluency rewriting. GrammarBot leads CWEB F0.5 by 2.99 points because its higher precision outweighs AmberPen's 3.02-point recall advantage on low-error-density text.
Speed
| Latency per CWEB sentence | AmberPen | GrammarBot Neural |
|---|---|---|
| p50 | 217 ms | 1,000 ms |
| p95 | 1,024 ms | 2,408 ms |
| p99 | 1,413 ms | 4,421 ms |
AmberPen is 4.6× faster at the median and has a substantially tighter tail, making it better suited to proofreading while a user is typing.
Which should you choose?
- Choose GrammarBot Neural when CWEB-style edit precision is the overriding requirement.
- Choose AmberPen for stronger fluency correction, lower latency, and incremental proofreading.
- Use your own representative texts before committing: JFLEG and CWEB measure complementary behaviors, not every production workload.
See Benchmarks & performance for methodology, scorer versions, and the full product table.
This page covers AmberPen and GrammarBot Neural head to head. If you are still shortlisting, the grammar checker API comparison reviews seven options side by side, and how grammar correction is measured explains why GrammarBot wins F0.5 here while losing on fluency.