408 Area Code: Silicon Valley's Number

The 408 area code is San Jose and Silicon Valley — most of Santa Clara County plus small slices of Alameda and Santa Cruz counties. Carved out of the Bay Area’s original 415 in June 1959, 408 has shared its footprint with the 669 overlay since November 20, 2012.

Count the tech switchboards and no code comes close. Apple answers in Cupertino, Netflix in Los Gatos, Nvidia and Intel in Santa Clara, Adobe, eBay, and Cisco in San Jose — and the startups, suppliers, and venture offices that orbit them dial out under the same three digits. That concentration shapes what a 408 number signals, and why the code’s history reads like a compressed history of the Valley itself.

Where the 408 area code works

408 and 669 cover San Jose — California’s third-largest city — and the ring of Santa Clara County communities around it: Santa Clara, Sunnyvale, Cupertino, Campbell, Milpitas, Los Gatos, Monte Sereno, Saratoga, Morgan Hill, San Martin, and Gilroy, plus a portion of Palo Alto and a small corner of Fremont. The footprint is compact but dense: one county holds the bulk of the world’s best-known technology headquarters.

Locally, “the 408” is San Jose shorthand — it shows up in team merch, event names, and the annual 408k road race. The code is a civic badge in a way few three-digit prefixes manage, which is exactly what makes it valuable on a caller ID.

1959: carved from the Bay Area’s original code

When area codes reached California in 1947, the state got three: 213 in the south, 415 in the center, and 916 in the north. Twelve years of postwar growth later, the phone companies split the center: in June 1959, the South Bay and Central Coast came out of 415 as the new 408.

The original 408 was a regional code, not a metro one. It ran from Sunnyvale and San Jose down the coast through Santa Cruz, Salinas, and Monterey — orchard country at the northern end, fishing and farm towns at the southern. The orchards, famously, did not stay orchards.

1998: the split that sent the coast to 831

Four decades of Valley growth forced the next cut. On July 11, 1998, under CPUC Decision 97-02-017, the coastal and agricultural south — Santa Cruz, Monterey, Salinas, Hollister — split off as the new 831 area code, with permissive dialing running until February 20, 1999. What stayed 408 was the Silicon Valley core: San Jose, Sunnyvale, Los Gatos, Gilroy, and their neighbors.

One landmark stayed on the 408 side of the line despite sitting far from any office park: Lick Observatory, on Mount Hamilton east of San Jose, kept its 408 number while the beach towns below changed codes.

669: the overlay that waited fourteen years

669 is one of telecom’s stranger stories: it was approved for San Jose twice, thirteen years apart. The CPUC first adopted a 669 overlay on November 19, 1998, in the middle of the dot-com number crunch. Thirteen months later — December 16, 1999, Decision 99-12-051 — the Commission suspended it indefinitely — one of six California overlay plans shelved at once — and bet on number conservation instead. Pooling, in place from 2001, stretched 408’s remaining prefixes for a decade.

The reprieve eventually ran out. By November 2010 only 47 prefixes were left, and on October 20, 2011 the Commission revived the overlay in Decision 11-10-031 — NANPA Planning Letter PL-430. Permissive 1+10-digit dialing began April 21, 2012; 1+10-digit dialing became mandatory on October 20, 2012; and 669 finally entered service on November 20, 2012.

Overlay mechanics worked as they do everywhere: no existing 408 number changed, and 669 fills new demand across the identical territory at identical cost. A 669 number is simply a newer San Jose-area line. Our guide to how area codes work unpacks the regulatory shift from splitting territories to stacking codes — and the stack has room: NANPA’s October 2025 exhaust analysis projects the 408/669 pool lasting into the mid-2050s, so no third code is on the horizon.

What a 408 caller ID actually tells you

Only that the number was issued in the San Jose area — not where the caller sits, and not who they are. Caller ID can be spoofed outright, and a code this rich in banks, employers, and IT departments is a natural costume for fake recruiter calls and “help desk” credential phishing. The reliable habit is the callback: hang up, look up the number the organization publishes, and place the call yourself. A legitimate 408 caller survives that test every time.

A San Jose number for your business

Selling into Silicon Valley means calling people who screen hard. A 408 or 669 number gives a vendor, recruiter, or service firm a San Jose front door — answered at rates an out-of-state code rarely matches, for reasons our local presence dialing guide breaks down. Rate centers, not office addresses, govern provisioning — a business anywhere can hold San Jose digits.

SIPNEX supplies San Jose DIDs in 408 and 669 alike, SIP trunking sized for outbound teams, and A-level STIR/SHAKEN attestation under our own carrier certificate — in a market where the person answering may well work in security, a signed call is the credential that holds up.

Frequently asked questions

SIPNEX is an FCC-licensed carrier providing local DID numbers in San Jose and every US market, toll-free numbers as a registered RespOrg, and dialer-grade SIP trunking — every call signed with our own STIR/SHAKEN certificate. Talk to an operator or call (833) 665-2220.