Popular tokens show up in Simple Base Swap out of the box. But Base has hundreds of thousands of tokens, and the long tail changes daily. For everything beyond the curated list, there is one universal mechanism: the contract address.
What a contract address is
Every token on Base is a smart contract living at a fixed address, a string starting with 0x. That address is the token's true identity. Names and tickers are just labels the creator typed in, and nothing stops two hundred different contracts from all calling themselves PEPE. Exactly one of them is the token people are actually trading; the address is how you tell them apart.
This is the single most important idea in this article: tickers can lie, addresses cannot.
How to add a token
In the swap screen, open the token selector and paste the contract address into the search field. The app looks the token up, shows you its name and symbol, and one tap imports it. From then on it behaves like any listed token: you can hold it, see its balance, send it and swap it.
Where to find the right address
Never take an address from a random comment, a DM or a screenshot. Use sources where the community has already done the verification:
The project's official website or documentation is the canonical source, assuming you reached the site through a known channel rather than an ad. Aggregators like CoinGecko and DexScreener list the contract address for every token they track, on Base and elsewhere, and a token with real volume on these platforms is at least a real, traded asset. Basescan, the Base block explorer, shows holder counts, liquidity and activity for any address, and a glance there quickly separates a living token from an empty shell.
Cross-check two of these sources and the odds of importing an impostor drop to roughly zero.
What importing does not mean
Adding a token to your wallet is bookkeeping, not endorsement. It makes the token visible; it says nothing about whether the token is a good idea. Anyone can deploy a token in minutes, including tokens designed so they can be bought but never sold. If a token exists only in a Telegram group and nowhere on CoinGecko, DexScreener or a functioning website, that absence is information.
And if a token you never bought is already sitting in your balance advertising a website, that is a different situation entirely; we wrote a separate guide about scam airdrops. The one-line summary: tokens you import after checking an address are tools, tokens that arrive uninvited with a URL in the name are bait.
A practical workflow
Find the token on CoinGecko or DexScreener, copy the Base contract address from there, paste it into the token selector, and confirm that the name and symbol the app resolves match what you expected. Ten seconds of care, once per token, and your custom list stays as trustworthy as the curated one.