Supply Curve Visualizer Screensaver
The Supply Curve Visualizer screensaver ticks a precise, live readout of Bitcoin's real circulating supply climbing toward its real 21 million hard cap, computed exactly from the current live block height via mempool.space. It's free, runs in your browser, and ESC exits.
Live preview
Press ESC to leave fullscreen. Settings are saved in your browser only.
How the Supply Curve Visualizer screensaver works
The saver fetches Bitcoin's real current block height from mempool.space, with no key required.
Circulating supply is computed exactly from that height using Bitcoin's real, fixed halving schedule.
Between real blocks, the readout interpolates smoothly at the real average ten-minute pace.
A progress bar shows how close real supply is to the fixed 21 million cap.
Why Bitcoin supply approaches 21 million asymptotically
Bitcoin’s issuance is written into its protocol. New coins come into existence only as the block subsidy paid for each block, and that subsidy is cut in half every 210,000 blocks, an event known as the halving. It started at 50 BTC in 2009 and fell to 25 BTC at block 210,000 in November 2012. Since blocks arrive on average every ten minutes, a halving takes roughly four years, though the exact timing depends on how much mining power is on the network.
Because each era issues half as much as the last, the total supply is a geometric series that converges just below 21 million. The final coins are expected to be mined around the year 2140, so the curve flattens rather than ending abruptly. Rewards are calculated in whole satoshis, each a hundred-millionth of a bitcoin, and the rounding at each halving puts the true ceiling at 20,999,999.9769 BTC.
It is worth being clear about what the figure is. It is the number of coins issued, not the number that can be spent. The first 50 BTC, from the genesis block, cannot be spent, and the readout reflects issuance only; it says nothing about price or demand.
A worked example
You'll see the real supply figure tick upward continuously — a genuine, exact computation from Bitcoin's known issuance rules, not an approximation.
Settings & tips
- Accent recolours the progress bar.
- The 21 million cap is a real, fixed protocol rule that cannot be changed by a single actor.
- Supply growth slows by half at every real halving, roughly every four years.
Frequently asked questions
- Is this exact?
- Yes — circulating supply is deterministic given the real current block height, computed precisely from Bitcoin's known issuance schedule.
- Is a key needed?
- No. mempool.space's public API is free and key-less.
- When does supply reach 21 million?
- Around the year 2140, per Bitcoin's real fixed halving schedule — this saver shows real progress toward that point.
- Is it free?
- Yes — free, no download, in your browser.
- Can the 21 million limit be changed?
- The limit is a rule of the Bitcoin protocol, so changing it would need the network to adopt new rules. In practice it is treated as a fixed part of the design.
- What happens to miners when the subsidy runs out?
- Once the subsidy ends, miners would be paid from transaction fees alone. How the network would fare under that model is a topic people still debate.
- Are lost coins subtracted from the number shown?
- No. The readout counts every coin that has been issued, computed from the block height, and has no way of knowing which coins are lost.