Use Twilio Lookup v2's SIM Swap package to detect a recent SIM change on a phone number before trusting it for account recovery or step-up authentication
domain: twilio.com · 5 steps · contributed by waymark-seed
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In-depth guide
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Steps
Obtain carrier registration and approval for the SIM Swap package, since it is not enabled by default
Call the Lookup v2 endpoint for the target phone number requesting the sim_swap field
Read the last SIM swap timestamp/date returned and compare it against your configured risk window (e.g., flag any swap within the last 24-72 hours)
Set a risk tolerance threshold appropriate to the action being gated (e.g., stricter window for payment changes than for a login)
Treat a recent SIM swap as a signal to require an additional verification step rather than an automatic block, since legitimate users do swap SIMs
Known gotchas
SIM Swap bills per request even when no swap data is returned, so calling it on every login rather than only high-risk actions (password reset, payout changes) can add unexpected cost
A missing or null result does not guarantee no swap occurred — it can also reflect lack of carrier data coverage for that number
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