A Private Key Is Just A Number
Every bitcoin is guarded by a number. Here is what that number is, how it turns into an address, and why the board keeps throwing them away.
Keys tried, speed and matches
Keys tried this session counts every key your browser has made and checked since you pressed Start. Each is a fresh random number turned into four addresses.
Keys per second is how fast every processor core on this device is going right now, added together.
Funded matches counts keys that turned out to control an address holding bitcoin, confirmed live with blockstream.info. Expect it to stay at 0.
Keys tried this session
0
Press Start to guess Bitcoin private keys.
0 keys per second
Funded matches 0
Every visitor so far
The running total of keys tried by everyone who has pressed Start on this site. Each browser reports a single number every 15 seconds and nothing else: no key, no address, no identifier.
Chance any of them hit is that total times the chance per key.
Every visitor so far
Counting
keys
Chance any of them hit: waiting for the total
Chance per key
How likely one random key is to control one of the million richest funded addresses. Each key makes four addresses, giving 1,270,100 comparisons against 2160 possible addresses.
Chance per key
1 in 1.2 × 1042
Like winning Powerball
The Powerball jackpot is 1 in 292,201,338. One key hitting is about as likely as winning that jackpot five draws in a row, with one ticket each time.
Like winning Powerball
5 times in a row
Expected wait
How long, on average, before one key hits at the speed shown: one divided by the chance per key times keys per second. Before you press Start it assumes 100,000 keys a second, a fast laptop.
Expected wait
3.6 × 1029 years
Ages of the universe
The expected wait divided by 13.8 billion years, the age of the universe so far. "Billion billion" means a billion times a billion.
Ages of the universe
26 billion billion
Latest guess
A key your browser made a moment ago, written in hexadecimal, and the legacy address it controls. Keys are shown for an instant and thrown away; they never leave the page.
The button asks blockstream.info, a public block explorer, about the address. Only the address is sent.
Latest guess
Random key, thrown away
Press Start guessing and every new key shows up here for a moment, then gets thrown away.
Address (for this key)
None yet
Count the digits
Big numbers stop meaning anything after a while, so here they are side by side. Your session is at the top. The thing it is trying to hit is near the bottom.
- Keys tried this session Press Start
- Keys tried by every visitor so far Counting
- Powerball jackpot outcomes 2.9 × 1089 digits
- People alive 8.2 × 10910 digits
- Age of the universe in seconds 4.4 × 101718 digits
- Grains of sand on every beach about 101920 digits
- Possible Bitcoin addresses 1.5 × 104849 digits
- Atoms in the Earth 1.3 × 105051 digits
- Possible Bitcoin private keys 1.2 × 107778 digits
- Atoms in the observable universe about 108081 digits
Why it never works
The board is the experiment. These pages are the explanation, for anyone who wants to check the numbers.
How It Works
What happens to every key, exactly which addresses are checked, and what leaves this page.
The Odds
Every figure on the board worked out, with your session's numbers updating as it runs.
Spot Check
Draw a random key and ask a public block explorer about all four of its addresses yourself.
Questions
- Can this site actually find someone’s bitcoin?
- No, not in any length of time that means anything. Each random key has about a 1 in 1.2 × 1042 chance of opening one of the richest funded addresses, so at 100,000 keys a second the expected wait is 3.6 × 1029 years.
- Is my computer really guessing keys?
- Yes. Your browser runs one worker for each processor core, and each one draws genuinely random 256-bit keys, turns every key into its four Bitcoin addresses and checks them against the list, as fast as the device allows.
- Does any key leave my browser?
- No. Keys are made, checked and thrown away inside the page. The only things sent anywhere are an address to blockstream.info when you press Check or a possible match needs confirming, one number every 15 seconds to the site’s counter, and page views with no identifier.
- What happens if it finds a funded address?
- The site shows the address and its balance, after confirming both live with blockstream.info. It never shows the key, and nothing on this site can move bitcoin.
- Which addresses does it check?
- The 1,000,000 richest funded addresses of the three kinds a single key reaches (legacy 1..., wrapped SegWit 3... and native SegWit bc1q...), holding 17,021,759 BTC, about 85% of all bitcoin, as of 14 October 2026.
- So how does bitcoin get stolen?
- By copying keys, never by guessing them. Coins are lost to keys that were not really random, phrases a person chose, malware, phishing and fake support agents. A key made properly at random by established wallet software is out of reach of every computer there is.
From the blog
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How Big Is 2256?
The number of possible keys, the number of possible addresses, and what the chance per key on the board actually measures.
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The Speed Problem
A laptop tries a hundred thousand keys a second. A data centre tries more. Here is why no amount of hardware gets the wait below the age of the universe.