What do the letter grades (A through F) mean?

SpiderRating letter grades map directly to SpiderScore ranges: A (9.0–10.0) means excellent, B (7.0–8.9) good, C (5.0–6.9) average, D (3.0–4.9) below average with known issues, and F (0–2.9) means critical security problems. Hard constraints can override the raw score — any critical vulnerability such as hardcoded credentials, command injection, or reverse-shell patterns forces an F regardless of other scores. As of March 2026 the ecosystem distribution is: A 0%, B 1.3%, C 69.4%, D 16.3%, F 13%, with an average score of 5.26/10.