How to use it
- Select Microphone or System or tab audio. Shared system audio depends on browser and operating-system support.
- Press Start listening and grant the requested permission.
- Place the threshold above background noise but below the active CW signal.
- Watch Peak tone, Signal, Timing, Live Morse, and confidence-colored decoded text.
- Use Clear to begin a new session or copy the decoded text for your own notes.
Decoder mechanics
The decoder analyzes audio locally in the browser. It searches a narrow 350-1000 Hz CW range, tracks the strongest stable tone, estimates its envelope, and classifies tone and gap durations against an adaptive Morse timing model.
Character colors express confidence from timing fit and signal stability. A low-confidence character is a warning, not a second hidden result. Audio is not uploaded or stored by CW599.
Accuracy and limitations
Best results come from a single clean CW tone with stable speed. Speech, music, multiple stations, fading, automatic gain changes, severe noise, or an off-frequency signal can split or join characters incorrectly. This browser tool is intended for practice and assistance, not safety-critical or regulatory use.
Versions and archives
v1.1 aligns the narrow-screen content gutter with the site header, without changing microphone permissions, local decoding, or audio handling. v1.0 introduced local microphone and shared-audio decoding, adaptive timing, live Morse, and confidence-colored output.
Changelog · September 7, 2026
Added consent-aware anonymous tool-open and applicable activity counters or durations. No leaderboard or change to the tool’s calculation, audio or CW Room communication identity was introduced. No audio, answers, location inputs or raw browser IDs are stored in analytics. Unique browsers are estimates, not people. Previously archived documentation remains available below; code history is retained in Git and private deployment backups.
Site changelog · Spanish support
September 20, 2026: the homepage, all eight Morse Lab tools and their current help pages now support Spanish. State, error, permission and optional leaderboard messages are localized; audio, scoring, identities and saved results are shared and unchanged. Guides, articles, shop, account and legal destinations remain in English and are labeled accordingly. Historical help keeps its original languages. Analytics recognizes Spanish routes and respects the same privacy choices without collecting new fields.
Site changelog · Japanese support
September 22, 2026: all eight Morse Lab tools and their current guides now support Japanese. The existing Japanese homepage and interface copy have been reviewed, including dynamic feedback, errors, accessibility, permissions and voluntary leaderboard publication. Audio, scoring, shared identities and saved results are unchanged. English, Chinese and Spanish remain available. Untranslated destinations are labeled as English. Existing Japanese Letter Trainer archives remain available; other historical guides retain their original languages. No new data fields or permissions are introduced.
Version archive
When a retired release has a runnable snapshot, this list will link both its documentation and the archived tool. Earlier releases without a snapshot are explicitly marked documentation only.