For most new DEXes, we recommend starting with a v2 architecture and custom fee tiers. Concentrated liquidity (v3) is justified if you clearly understand how LPs will manage positions and are prepared for a more complex audit.

What Do We Customize in the Fork?

Fee structure. In Uniswap v2, the fee is fixed at 0.3%, with 0.05% as protocol fee. In a fork you can:

• Change the base fee (e.g., 0.1% for stablecoin pairs, 1% for exotic tokens)
• Add dynamic fees based on volatility (requires an oracle or TWAP)
• Direct the protocol fee to a DAO treasury, staking, or token buyback
• Add referral fees: part of the commission goes to a referrer (requires a mapping referrer → address)

Token-specific restrictions. Often you need pairs only between approved tokens (permissioned factory) or to restrict pool creation without multisig confirmation. This is added via mapping(address => bool) public allowedTokens and a modifier in createPair.

Price oracles and TWAP. Uniswap v2 stores cumulative prices for TWAP — built into _update(). A fork can add more frequent snapshots or integrate Chainlink for manipulation protection. The original TWAP's weakness: with low liquidity, short TWAP windows (~5 minutes) are vulnerable to price manipulation via large swaps.

Why Are 90% of Forks Vulnerable to Flash Loan Attacks?

The error in forks: changing the fee logic breaks the invariant calculation. Uniswap v2 checks the invariant after all operations in a transaction:

require(balance0Adjusted * balance1Adjusted >= uint(_reserve0) * uint(_reserve1) * 1000**2); 

If balance0Adjusted is incorrectly calculated due to a non-standard fee, an attacker can drain the pool through a series of flash swap → swap back transactions, each passing the check but collectively removing liquidity. We have discovered this bug in three forks on BSC, leading to losses of $1.2M, $800k, and $3.5M.

Any change to fee logic requires mandatory invariant-based fuzz tests in Foundry: Echidna or Foundry's vm.assume with hundreds of thousands of random parameters. Invariant: k_after >= k_before * (1 - fee).

Fee-on-transfer tokens. If the DEX targets tokens with a tax, the standard Uniswap v2 does not work correctly: the contract expects to receive amountIn tokens but receives amountIn * (1 - tax). The functions swapExactTokensForTokensSupportingFeeOnTransferTokens already exist in Uniswap, but minimalist forks often discard them, breaking compatibility with popular BSC tokens.

How We Test and Deploy the Fork

Smart contract development — Foundry for everything: tests, deployment, fuzzing. We base our work on the official Uniswap v2-core + v2-periphery repositories as submodules to clearly see the diff. Changes are minimal and focused — we do not rewrite what works.

Tests. For a fork, the minimal set includes:

• Creating a pair, adding/removing liquidity
• Swaps in both directions with invariant check
• Flash swap with correct and incorrect return
• Fee calculation for non-standard values
• Fuzz tests on the invariant with 100k+ iterations
• Fork tests on mainnet: real tokens, real balances via vm.createFork

Frontend. We adapt the Uniswap Interface (open-source) or build from scratch using React + wagmi + viem. The Uniswap SDK v3 is compatible with v2 forks with proper chain and factory address configuration.

Aggregation router. If multi-hop routing through your own pools plus external DEXes is needed, we integrate the 1inch Aggregation Protocol or write a custom router. This is important for UX: users should not manually search for routes.

Timelines and Development Stages

What's Included in the Work?

• Engineering documentation detailing deviations from the original protocol
• Testnet and mainnet deployment, including multisig (Gnosis Safe) setup
• Source code with CI/CD, linters, and test coverage >90%
• Training your team on working with the fork and deploying new pools
• 30-day post-launch support

Step-by-Step Fork Customization Plan

1. Requirements analysis and base version selection (v2/v3)
2. Fork the repository and create a submodule for the original code
3. Implement changes to contracts (fee, factory, router) while preserving the diff
4. Write and run tests, including fuzz and fork tests
5. External security audit
6. Testnet deployment and integration testing
7. Mainnet deployment with multisig and liquidity setup

How Long Does Development Take?

Timelines depend on customization complexity: a v2 fork with modified fee tiers takes 1-2 weeks of development plus 2-4 weeks of auditing. A full v3 fork with a custom UI starts from 2 months. For a production protocol, auditing by an external team is not optional. We guarantee transparency at every step — our experience: 10+ years in blockchain development (5+ years in DeFi), 40+ deployed smart contracts, and 20+ audited AMM forks. Request a consultation — let's discuss your project.