GasClock

When is Ethereum gas cheapest?

A single static page that answers that question using seven days of on-chain data.

Most gas trackers show you the price right now. That is the least useful number on the page, because you cannot change the past — you can only decide when to send a transaction. GasClock samples roughly 670 blocks across the last week and lines them up by hour-of-day and day-of-week, so the cheapest windows are visible at a glance.

• Reads the EIP-1559 baseFeePerGas straight from Ethereum block headers
• Samples one block every ~15 minutes for the last 7 days (~670 samples)
• Aggregates into a 7 x 24 heatmap of average base fee
• Highlights the cheapest and most expensive hour of the week
• Renders a 24-hour bar chart of average gas by hour
• Lets you switch between UTC and your local timezone

No wallet connection. No signup. No analytics. No API keys. No build step.

Public JSON-RPC endpoints, no authentication required:

• https://ethereum-rpc.publicnode.com
• https://rpc.flashbots.net

Blocks are fetched in batches of 30 via eth_getBlockByNumber. Each block header carries both the timestamp and the base fee, so a single request yields everything the heatmap needs.

Sampling is deliberate: an earlier version used eth_feeHistory to pull all ~50,000 blocks in the window, which meant ~50 heavy requests. Public nodes rate-limit that hard. ~23 light batched requests for ~670 samples gives the same shape for a fraction of the load.

Requires Python 3.9+ and nothing else.

python scripts/fetch_gas.py

That writes data/gas.json. Then serve the folder over HTTP — opening index.html directly will not work, because fetch() is blocked on file:// URLs:

python -m http.server 8099

Open http://127.0.0.1:8099.

The repo is designed to run for free with no server:

1. Push to GitHub.
2. Enable GitHub Pages for the repository root.
3. The included workflow (.github/workflows/update.yml) refreshes data/gas.json every 15 minutes and commits the result, which Pages then serves.

Total running cost: zero.

• Mainnet only. Rollups (Base, Arbitrum, Optimism, and friends) have separate fee markets and are not reflected here.
• Base fee only. Your wallet adds a priority tip on top. This page does not track tips, so the numbers are a floor, not a total.
• It is a summary, not a forecast. Everything here already happened on-chain. Nothing on this page predicts future gas prices.
• The heatmap is a rolling window. A single unusual event — an NFT mint, an airdrop claim — can skew a cell.

MIT. See LICENSE.