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Uniswap Skim

Uniswap Skim is an open-source JavaScript command-line tool that scans Ethereum Uniswap V2 pair contracts for positive differences between actual token balances and stored reserves, which may be claimable through the protocol’s skim function.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Uniswap Skim — OpenViST project profile in DeFi.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use it when you want a terminal-based scan of Uniswap V2 pair contracts for potential skim opportunities and can provide the expected Ethereum node connection.

Who it is for

  • Developers who can work with JavaScript scripts and an Ethereum node.
  • Technically experienced DeFi users investigating Uniswap V2 balance-reserve discrepancies.

Documented uses

  • Update a local log of newly deployed Uniswap V2 markets.
  • Search logged pairs for positive token balance-reserve differences.
  • Review token and pair details and, where available, an estimated token value.
Before you choose

Requirements & limits

The repository is public and identifies its license as Unlicense. The scripts are command-line tools.

  • The scripts default to a local Ethereum node with a WebSocket connection on port 8546; using another port or a service such as Infura requires code changes.
  • The scanner uses a configurable minimum dollar value and attempts CoinGecko price lookup, but still returns values when a token price is unavailable.
  • The README cautions that discrepancies can be too small to justify transaction gas and that direct calls from an externally owned account may be frontrun.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Install and scan Uniswap V2 pairs

Set up the scripts and run a scan for positive balance-reserve discrepancies.

Before you start

  • A cloned copy of the repository
  • Node.js and npm to install the listed dependencies
  • An Ethereum node with a WebSocket connection; the scripts default to a local node on port 8546

Steps

  1. Clone the repository and change into its directory.

  2. Run the command below to install the web3 and axios dependencies.

    Documented command
    npm i

  3. If needed, edit the code to use a different node or port.

  4. Run the command below from the repository root to update the market log.

    Documented command
    npm run update

  5. Run the command below from the repository root to scan logged markets.

    Documented command
    npm run skim

Expected outcome

The scripts print pair and token details, including detected imbalances; they attempt to retrieve token prices through CoinGecko.

Guide limitations

  • Scanning thousands of pairs can take several minutes.
  • The default minimum displayed dollar value is $0.01, but discrepancies are also returned when CoinGecko has no token price.
  • A detected discrepancy may not cover the gas cost of claiming it, and the README warns that direct calls from an externally owned account may be frontrun.
  • The scanner ignores cases where a token’s reserve is higher than its balance.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
Source record details
Source availability
Active
Sources checked
15 October 2026
Original website title
nicholashc/uniswap-skim · Official homepage title · retained in its source language
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