A swap is a disposal. Trading one token for another is a taxable event in most regimes even though no fiat moved — this is the single most expensive misunderstanding in crypto.
Income and gains are different. Staking rewards, airdrops and mining are usually income at receipt, and the value at receipt becomes the basis for a later disposal.
Records beat reconstruction. Dates, amounts, fiat value at the time and the wallet involved. Rebuilding this after the fact, across venues that have since closed, is the part people underestimate.
Moving between your own wallets is not a disposal — but the basis and the acquisition date must travel with the lot.
Why this is computed on your device
A complete transaction history is the most revealing data set an individual holds: counterparties, balances, timing, habits. DexLadder's ledger runs in your browser and uploads nothing, which is why there is no account to create and nothing to breach.