Clash of Clans – Can People Steal Loot in My Treasury?

Until you reach Town Hall 5, 20% from your gold/elixir can be stolen from the storages. The cap for this is 200k. From TH6 and onwards, this percentage drops by 2% for each TH level. From TH7 and above the cap increases with 50k for each TH level.

So for clarity and completeness (and no calculations):

TH Level    % Available to be Stolen    Cap    Storage Amount to Reach Cap
1-5         20%                         200k   1.000M
6           18%                         200k   1.1111M
7           16%                         250k   1.5625M
8           14%                         300k   2.1428M
9           12%                         350k   2.9167M
10          10%                         400k   4.0000M

According to Supercell:

Strength is based on each member’s attacking power (troops, army camp capacity, spells and heroes) and defensive strength (defense buildings, walls, traps and heroes). Different layouts and base designs do not affect strength. The only way a member’s strength can be changed is if they upgrade their troops, defenses, spells, etc.

Another quote:

Once a match is found, players are sorted on the map from strongest to weakest, in terms of defence power of their base, i.e., defense levels, hero levels, traps, etc. We do not take TH levels into account. Instead, we only use overall strength of all defence elements in player’s village. For example, a TH8 with higher level defenses than a TH9 will be ranked higher than the TH9 in the war map. XP has no bearing on the ranking of your war base on the war map

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