May I ask how to increase the upper limit of the backpack

bonwborn

May I ask how to increase the upper limit of the backpack,The backpack always fills up quickly

SilverBride

Buy upgrades from the bag vendor.
Buy storage increases on you mount training.
Subscribe to ESO+ for the craft bag so all mats go into it.
You can also buy bank storage upgrades.

Ilsabet

The main way to increase a character's backpack space is by spending gold at Pack Merchant NPCs in towns. Each upgrade gives you 10 more slots and costs an increasing amount of gold each time.

You can also do daily horse training at Stablemaster NPCs. This can be done once per day for 250g each time, and gives 1 slot each time up to 60 slots.

If you don't mind spending real money, there are also certain non-combat pets available in the Crown Store that add 5 inventory slots just for owning the pet.

You can also ease your character's burden by putting items into the bank, by visiting the bank NPC in towns. This bank storage can be accessed by all characters on the account, so if you want you can create more characters and have them hold items that your active character may not always need to have access to.

Having an ESO+ subscription doubles the number of slots in your bank storage but doesn't affect individual characters' backpacks, so that may or may not be what you're looking for.

DinoZavr

There are only 3 things you can do:
1) + 80 upgrade backpack capacity for gold using pack merchants (180K) https://en.uesp.net/wiki/Online:Pack_Merchants
2) +60 train your mount capacity (15K), Crown Store capacity upgrades speed up the process but they are too costly
3) +15 - each of 3 "inventory" pets you buy from Crown Store (when they are available) increases bag capacity by 5 slots
considering you start with 60 slots, 215 is the current maximum

ESO+ does not affect backpack capacity, though it doubles bank space,
it also offloads your bag, because raw crafting resources and ingredients, decon, stylestones and traitstones go to Craftbag.
also you can "offload" things into housing storage containers (360 slots total) you buy from Master Writs vendor for Master Writ vouchers (or for TelVar, but this option is kinda expensive).
Also you can consider Bank and Merchant assistants you can summon "in the fields" to bank/sell thing, and Deconstruction assistant (when you have ESO+ materials from deconstruction will go directly to a Craftbag)
One more good option for PC players is the JunkBuster addon, though you would have to make appropriate filters
(it helps me a lot as i set it to autodestroy stolen food ingredients, stolen cloth, stolen 40g treasures, 1g gear, etc - to be destroyed immediately on them picking up).