If by "safest PLB" you mean the Personal Locator Beacon most likely to get you detected quickly and give you confirmation that the alert was received, here’s a short, practical answer plus the key reasons and top model picks by use case.

What makes a PLB “safe”

• Uses the government COSPAS‑SARSAT 406 MHz network (global, no subscription). (fcc.gov)
• Has integrated GNSS (GPS/Galileo/etc.) so position is sent immediately (much faster fix). (oceansignal.com)
• Return Link Service (RLS) capability — beacon receives an acknowledgement that COSPAS‑SARSAT has received and localized your alert (does NOT mean rescue is launched, but gives critical confirmation). RLS is now authorized in the U.S. and widely supported. (sarsat.noaa.gov)
• For maritime use, AIS alerting lets nearby vessels see you on their plotters (very helpful at sea). (oceansignal.com)
• Robust battery life, waterproofing/buoyancy, an IR/visible strobe and a 121.5 MHz homing tone are all important for final local pickup. (oceansafety.com)

Top safe PLB picks (2024–2025, by common expert/ manufacturer lists)

• Best overall (land & sea, with RLS/confirmation): ACR ResQLink View (RLS model). Digital display + RLS acknowledgement, multi‑GNSS, long operational runtime and built‑in buoyancy — strong safety feature set. (locatorbeacons.co.nz)
• Best for offshore/marine (AIS + RLS): Ocean Signal rescueME PLB3 AIS. Sends 406 MHz distress + AIS to nearby vessels + 121.5 homing + RLS + NFC app diagnostics — excellent for getting both local and global assets alerted. (oceansignal.com)
• Best very compact / longest battery (simple, proven): Ocean Signal rescueME PLB1 — extremely compact, 7‑year battery, GNSS, 24+ hr transmit, proven COSPAS‑SARSAT operation. Good for hikers who want minimal weight. (oceansafety.com)
• Reliable budget/basic pick: McMurdo FastFind 220 — GNSS (GPS + Galileo), 6‑year battery, floats in pouch, MEOSAR compatible; solid, no‑frills PLB. (seasofsolutions.com)

Important tradeoffs / notes

• PLBs are SOS-only devices (one-way distress) — they do not offer two‑way messaging or coordination the way satellite messengers (Garmin inReach, Zoleo, etc.) do. If you want two‑way comms to triage an incident or stay in touch, carry a satellite messenger in addition to (or instead of) a PLB. PLBs shine when you need the highest-power, government‑monitored distress signal. (Garmin.com)
• RLS gives confirmation that your alert was received and located, but it is not proof that rescue is underway. RLS greatly improves user confidence but doesn’t replace good trip planning. (sarsat.noaa.gov)

What you should do after buying a PLB (to maximize safety)

• Register it immediately (NOAA SARSAT beacon registry in the U.S.; keep registration up to date). Registration is free and critical. (sarsat.noaa.gov)
• Note the battery expiry and follow manufacturer service/battery‑replacement instructions (battery replacement usually requires sending the unit to a service center). (oceanmedix.com)
• Practice the self‑test procedure (most units have a non‑safety self‑test) and check status before trips. (BOATTEST.com)
• If you’re primarily offshore, favor AIS + RLS models; if primarily solo backcountry, favor a compact GNSS + RLS PLB or pair a PLB with a two‑way satellite messenger.

If you want, I can:

• Give a current price comparison for any of these models (I’ll check live listings), or
• Narrow the recommendation to a single “safest” model for your exact use (hiking, kayaking, offshore sailing, flying) and show where to buy and how to register.

Which option would you prefer?