Mumbai Metro's baggage rules are standard for the most part, but there's one genuinely useful tip here if you're travelling with real luggage.
Standard limits
You can carry up to 25 kg, sized within 80 × 50 × 30 cm, for free. Between 25-32 kg is still allowed, but attracts an extra charge - the exact fee wasn't published anywhere we could verify, so ask at the counter if you're near that limit.
If you've got a big suitcase, prefer Line 3
This is the tip most guides miss: Line 3 has newer, larger X-ray scanners than the older Lines 1, 2A, and 7, and comfortably handles bigger bags - up to roughly 23 kg and larger dimensions - without the friction travelers report on the older lines. If you're heading to or from the airport with check-in-sized luggage, routing through a Line 3 station will save you hassle at security.
What's banned
- Inflammables of any kind
- Pets
- Raw meat or fish
- Sealed liquor bottles are allowed to carry, but you can't drink on the metro
- Food can be carried on, but not eaten onboard
Bottom line
Standard bags under 25 kg move through any line with no issue. If you're carrying something bulkier - especially heading to or from the airport - route through a Line 3 station rather than the older lines to avoid a slower security check.