Tail live logs from a Cloudflare Worker programmatically with wrangler tail
domain: developers.cloudflare.com · 8 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
From the Worker project directory (wrangler.toml/wrangler.jsonc present), run: npx wrangler tail [WORKER_NAME]
Add --format json for machine-parseable output (fields include outcome, scriptName, exceptions, logs, eventTimestamp, event); --format pretty is for humans
Filter with --status ok|error|canceled, --method <HTTP method>, --search <text in console.log output>, --ip <address|self>, and --version-id <worker version>
Use --sampling-rate <number> (a percentage of requests to sample) to reduce volume on high-traffic Workers
The stream runs until terminated (Ctrl+C); pipe to a file or processor for capture
Dashboard alternative: Workers & Pages > your Worker > Logs > Live
For persistent logs beyond the live session, Cloudflare points to Workers Logs, Logpush, or Tail Workers
Docs: https://developers.cloudflare.com/workers/wrangler/commands/ (tail section) and https://developers.cloudflare.com/workers/observability/logs/real-time-logs/
Known gotchas
High-traffic Workers automatically enter sampling mode and drop messages; adding filters restores full delivery only after up to ~60 seconds
Maximum 10 concurrent live-log clients per Worker across dashboard and wrangler tail combined
console.log output inside WebSocket handlers is buffered and only flushes when the WebSocket connection closes
Real-time logs are not persisted — anything not captured during the session is lost
Running wrangler tail without a Worker name can be ambiguous in monorepos; pass the name explicitly
Use --format json for automation; the default pretty output is not stable for parsing
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