Google Flights - deep-link any search via `tfs` (incl. multi-city)

Use a search URL for routes that fit the schema below. Use the visible controls for filters that the schema does not cover:

https://www.google.com/travel/flights?tfs=<base64 protobuf>&hl=en&curr=USD

tfs contains a serialized protobuf encoded as URL-safe base64 without padding.

Schema

Query {
  repeated Leg legs   = 3;
  repeated int32 pax  = 8;   // one entry per traveler: 1=adult 2=child 3=infant-in-seat 4=infant-on-lap
  int32 seat          = 9;   // 1=economy 2=premium economy 3=business 4=first
  int32 trip          = 19;  // 1=round trip 2=one way 3=multi-city
}
Leg {
  string date  = 2;          // "YYYY-MM-DD"
  Airport from = 13;
  Airport to   = 14;
}
Airport { string code = 2; }  // IATA airport OR city code

Multi-city = trip=3 plus one Leg per segment, in order. Open-jaw is just a 2-leg multi-city where leg2's origin != leg1's destination.

Minimal encoder (no protobuf dep):

import base64
def vint(n):
    o=b""
    while True:
        b_=n&0x7F; n>>=7; o+=bytes([b_|(0x80 if n else 0)])
        if not n: return o
def s(f,v): v=v.encode() if isinstance(v,str) else v; return vint(f<<3|2)+vint(len(v))+v
def v(f,n): return vint(f<<3)+vint(n)
def leg(d,a,b): return s(2,d)+s(13,s(2,a))+s(14,s(2,b))
def tfs(legs, seat=1, trip=3, passengers=(1,)):
    passengers = tuple(passengers)
    if seat not in (1, 2, 3, 4) or trip not in (1, 2, 3):
        raise ValueError("Invalid seat or trip code")
    if not passengers or any(p not in (1, 2, 3, 4) for p in passengers):
        raise ValueError("Use passenger codes 1, 2, 3, or 4")
    body = b"".join(s(3, leg(*item)) for item in legs)
    body += b"".join(v(8, p) for p in passengers) + v(9, seat) + v(19, trip)
    return base64.urlsafe_b64encode(body).decode().rstrip("=")
 
tfs([("2027-03-10","JFK","LHR"),("2027-03-24","CDG","JFK")])

The examples append &hl=en&curr=USD for English and US dollars. Use the user's requested locale and currency when they differ. The extraction example below assumes US dollars.

Verify the URL parsed correctly by reading page_info()["title"] - it echoes "<Origin> to <Destination> | Google Flights". A malformed tfs silently falls back to a blank search form.

Reading results

No login needed. Results render ~5-8s after wait_for_load(); poll rather than assuming. Every row is an <li>; the whole itinerary is in li.innerText:

js("""(()=>{const o=[];document.querySelectorAll('li').forEach(l=>{
  const t=l.innerText; if(t&&/\\$\\d/.test(t)) o.push(t.replace(/\\n+/g,' | '));
});return JSON.stringify(o)})()""")

This returns candidate text, including possible nested detail rows. Inspect the visible flight cards before counting or quoting results. Do not discard rows by text length because valid itineraries can contain long descriptions.

Multi-city flow quirks

• The first results page lists leg 1 only. The price on each row is labelled entire trip and is Google's estimate of the cheapest complete itinerary containing that leg.
• Clicking a leg-1 row navigates (title flips to "<Leg2 origin> to <Leg2 dest>") and shows the leg-2 options compatible with that leg 1 - usually restricted to the same alliance, so the set is small (3-6 rows).
• The leg-1 entire trip estimate can be below any actually selectable total. Observed a leg-1 badge of $1,073 whose cheapest real leg-2 pairing was $1,107. Always click through and read the leg-2 page for a bookable number.
• After clicking through, the <li> list needs another ~6s; an immediate query returns COUNT 0. Re-query rather than concluding there are no flights.
• history.back() returns to the leg-1 list with state intact.

Sorting / expanding

The observed multi-city pages had no Show more flights button. Check the current page for additional results before treating the visible list as complete. To sort:

js("[...document.querySelectorAll('button,div[role=button]')].find(x=>/Sorted by/i.test(x.innerText))?.click()")
# then
js("[...document.querySelectorAll('[role=menuitem],li')].find(x=>x.innerText.trim()==='Price')?.click()")

Verify the visible sort selection after each click. If the control is absent, wait for rendering and retry. Menu options: Top flights, Price, Departure time, Arrival time, Duration, Emissions.

Cabin comparison

Re-request the same legs with seat=2/3/4 rather than touching the cabin dropdown. Mixed-cabin itineraries are labelled in-row (Economy + Premium Economy, Business Class + Economy) and are frequently the cheapest hit in a premium search - read that suffix before quoting a fare.

Multi-city vs. two one-ways

Worth running both; they differ a lot. Same dates/route sampled 2026-07-25: multi-city open-jaw $1,107 vs. two separate one-ways $640 + $844 = $1,484. Multi-city won by ~25%. Encode the one-ways with trip=2 and a single leg.

Traps

• Chrome's CDP consent dialog can block the harness against the user's main profile. Google Flights needs no session state, so launching a throwaway Chrome with --user-data-dir=<tmp> --remote-debugging-port=<port> and pointing BU_CDP_WS at it is a clean workaround.
• Verify the displayed passenger count and total before quoting a fare. Check bag fees separately.

flights-multi-city.md · updated Oct 9, 2026 · 745 words