0x Swap or Gasless API: choosing the product

The 0x Gasless product changes how execution is submitted and paid for; it is not simply the regular Swap product with every cost removed. Choose it after checking the input asset and approval path.

The official FAQ distinguishes gasless swap execution from gasless approval. It says the Gasless API cannot directly sell a chain's native coin, and gasless approvals depend on token permit support. A user holding ETH or BNB therefore presents a different onboarding case from one holding an already-approved token.

Questions to answer in order

1. Is the selected chain supported by this product?
2. Is the sell asset eligible for the intended gasless flow?
3. Does the account already have the necessary allowance, or can the token authorize it through a supported permit?
4. Who bears execution cost, and where is it reflected?

0x explains that it can advance network fees and recover cost through the trade, with application sponsorship as another arrangement. The user may avoid keeping the native coin for execution while still bearing an economic cost in the trading asset.

Why a native-coin fallback matters

If your interface accepts native assets, do not silently transform every request into a gasless one. Wrapping a coin first changes the steps and may need its own transaction. A conventional Swap path can be the clearer product choice when the user already has native gas and wants a direct transaction workflow.

Check the product support matrix rather than reusing a general chain list. Successful support for one API does not imply successful support for another.

Describe the experience precisely

Tell users whether they are authorizing an approval, a trade or both. Do not promise a one-step experience until the account's actual state is known. A product that labels the setup honestly can be easier to use than one that advertises gasless trading and reveals an unexplained paid approval afterward.

If the user needs an exact output

The current Swap FAQ documents Exact Buy: the requested buy amount is exact, while the maximum sell amount is a spending ceiling. If execution needs less input, excess sell token returns to the taker. This differs from selling a fixed input with a minimum acceptable output. Verify the selected product and interface expose Exact Buy before promising it to a user; ordinary Gasless eligibility does not by itself establish that capability.