Largest by program count and bounty pool. Hosts the DoD VDP + many Fortune 500 + frontier model labs. Has 'Hacktivity' (publicly disclosed reports) — best place to learn what a good write-up looks like.
::start → Sign up free. Read 50 public reports in your favorite vuln class. Pick a program with broad scope and public engagement. Spend 4 hours reconning before you write a single payload.
Second-largest. Strong on private invite programs once you build a track record. Bug Bash events (paid live-hacking competitions) for senior researchers.
::start → Same as HackerOne. Their educational content (Bugcrowd University, free on YouTube) is excellent on web vulnerability categories.
European-headquartered. Strong roster of EU enterprise programs. Excellent CTF program ('1337up Live'). Often higher signal-to-noise than the US platforms.
::start → Free signup. Their public CTF challenges are a low-stakes intro to their platform mechanics.
French-headquartered. Strong on EU government + critical-infrastructure programs that aren't on US platforms. Multilingual.
::start → Free signup. Read their published Dojo training material first.
Vetted invitation-only researcher pool. Customers pay Synack, Synack pays the researchers. Higher pay per finding, harder to get in (technical interview + background check).
::start → After you have 50+ valid findings on HackerOne / Bugcrowd. Not an entry path.
US DoD's public Vulnerability Disclosure Program on HackerOne. Hosted at hackerone.com/deptofdefense. You report bugs in DoD-controlled .mil websites within scope. NO bounties — just public credit + the satisfaction of helping defend US systems.
::start → Read the scope. The scope is wider than people think. Submit a real finding. People have used DoD VDP submissions as resume credentials for federal cyber roles.