This is the first in a new pair of videos I’m running on apis.io — a profile of a provider, followed by an onboarding walkthrough of the same provider. First up is 0x, the institutional-grade DEX aggregation and crypto liquidity infrastructure that quietly powers token swaps inside hundreds of consumer wallets, exchanges, and onchain apps.
In the walkthrough I start where I always start — the 0x provider page on apis.io — and then click out into the live 0x developer area to see how the catalog lines up with what they actually ship.
Five APIs on the surface
The 0x catalog resolves into five distinct APIs, and the split is worth paying attention to because each one is a different job:
- Swap API — the core. Institutional-grade DEX aggregation that returns indicative prices, firm quotes, and ready-to-sign transaction calldata across 150+ liquidity sources on 20+ EVM chains. Two allowance models: the simple AllowanceHolder pattern and the gas-optimized Permit2 flow.
- Gasless API — lets end users swap without holding the chain’s native gas token. Fees come out of the sell token via a Permit2 meta-transaction signed off-chain and relayed to the Settler contract. This is the one that quietly removes the biggest onboarding cliff in DeFi.
- Cross-Chain API — any-token, any-chain bridging (private beta) with streaming quote updates, status, and history across Across, Relay, Bungee, CCIP, Circle CCTP, NEAR Intents, and more — spanning EVM plus Solana, HyperCore, and Tron.
- Trade Analytics API — read-only history of your Swap and Gasless trades with surplus, fees, route, and per-trade settlement detail. This is the monetization-and-reconciliation surface most aggregators forget to expose.
- Sources API — a reference endpoint listing the live liquidity sources currently routed against for a given chain.
Four products plus a reference API, settled by the 0x Settler smart contracts using the Permit2 standard, all behind a single unified API key.
What’s around the APIs matters as much as the APIs
The thing I keep emphasizing in these profiles is that the contract is only part of the story. 0x backs theirs up with a genuinely deep developer surface — documentation, a developer portal, pricing, an engineering blog, a changelog, a status page, supported-chains reference, an FAQ, and a bug bounty. And notably for where the industry is heading, a full develop-with-AI track: an official Agent Skill, an MCP server, a CLI, autonomous agent payments via x402, and an AI project showcase.
On the apis.io side, the 0x profile indexes more than the OpenAPI — there’s a Spectral governance ruleset (27 rules), a JSON-LD context (45 classes), a vocabulary, plans, rate limits, a FinOps profile, and 10 runnable code examples. That’s the kind of footprint that makes a provider legible to both humans and agents.
The data behind the profile
Everything you see on the apis.io profile is generated from an open, versioned APIs.json index. You can read the raw provider data — OpenAPI specs, rules, vocabulary, examples, plans — in the GitHub repo: github.com/api-evangelist/0x. If 0x ships something new, that’s where the change lands first.
0x currently scores in the developing band on apis.io — perfect discoverability and solid operational transparency, with developer ergonomics being the area with the most room to grow. That’s exactly the kind of read this series is meant to surface: not a grade, but a map of where a provider is strong and where there’s work left.
Next: onboarding
Profiling tells you what’s there. The companion video gets hands-on and actually signs up, creates an app, pulls an API key, and makes the first call — Onboarding with 0x — From Signup to Your First Swap Call.
Walk the full surface yourself on the 0x provider page, and watch the rest of the series on YouTube @APISearch.