Altcoin
Alts · Alternative coins · Altcoins
Any cryptocurrency other than bitcoin; the word is short for "alternative coin".
Simple explanation
Background: Korean investors say 알트코인, or just 알트, and call small, obscure coins 잡코인 ("junk coins"). Korea's exchanges are unusually altcoin-heavy: most of the money traded there goes into coins other than bitcoin and ether.
"Altcoin" stands for "alternative coin" and covers every coin that is not bitcoin. The word caught on after bitcoin's 2009 launch, when Namecoin (April 2011, built on bitcoin's code) and Litecoin (October 2011) appeared as alternatives to it. Today it spans everything from big networks such as Ethereum, XRP and Solana down to coins that barely trade.
Definitions vary. In the broadest sense ether and stablecoins such as Tether (USDT) are altcoins too, but market analysis often treats Ethereum (launched July 2015) separately and leaves out stablecoins, whose price is tied to $1. Altcoins also differ wildly from one another: native coins of smart-contract blockchains, service tokens issued on top of them, dollar stablecoins and meme coins made for fun all share the label, so "altcoin" on its own says nothing about how risky a coin is.
The size of the altcoin market is usually read backwards from bitcoin dominance, bitcoin's share of the total crypto market cap: when dominance falls, altcoins' share has grown. A stretch when altcoins clearly outrun bitcoin is called "altcoin season" or "altseason". One widely followed index calls it altcoin season when at least 75% of the top 50 coins by market cap, leaving out stablecoins and asset-backed tokens, have beaten bitcoin over the last 90 days. Nobody knows when such a stretch will come; the index only describes past performance.
Altcoins usually have smaller market caps and thinner trading than bitcoin, so their prices swing much harder. When bitcoin falls 10%, altcoins often fall further, and the same goes for rallies. Coins with a foundation or team behind them can be badly shaken if the business stalls, a hack happens or more tokens are released than planned, so circulating supply and token unlock schedules matter too. Korean exchanges designate coins with problems like these as investment warnings and, depending on the review, may end trading support.
Korea's market leans heavily toward altcoins. In an October 2023 analysis by the data provider Kaiko, bitcoin made up only 9% and ether 2% of Upbit's volume, against 36% and 22% on Coinbase in the US. Kaiko data reported in April 2026 again put about 85% of Korean volume in coins other than bitcoin and ether. Since July 19, 2024, Korean exchanges have reviewed listings under a shared "best practice" for trading support, and they re-check coins already trading every quarter.
Kimchi premiums also run wider and jump more often on altcoins. Bitcoin trades heavily and moves easily in and out of Korea, so its premium is fairly steady; an altcoin's premium can blow out to tens of percent on its own right after a listing, while deposits or withdrawals are suspended for wallet maintenance, or when its order book is thin. The same coin can carry different premiums on different Korean exchanges, and sometimes two coins share a ticker but are not the same coin at all, which makes the comparison simply wrong. When you move an altcoin between exchanges, check the withdrawal network too: exchanges support different networks, and a transfer on the wrong one can be hard to recover.
CoinGaja's Kimchi premium by coin table covers the top 120 Binance-listed coins by Upbit 24-hour trading value plus the coins inside that top 120 that Binance does not list (about 150 coins), and the list is redone every 10 minutes; nearly all of them are altcoins. A coin Binance does not list is compared with the first of OKX → Bybit → Bitget → Gate that trades it, and the table names the exchange used. Each coin's headline premium is the median of the four Korean exchanges; a same-ticker pair whose names and prices differ sharply is treated as two different coins and not compared with Binance; and a coin whose premium could shift by more than 1 percentage point from tick size alone has its premium hidden. The Price and premium heatmap shows altcoins' 24-hour price change and premium at a glance, and the BTC share (비트 점유율) in the top bar is bitcoin dominance.
Example
Total crypto market cap ₩3,000 trillion (about $2.1 trillion), of which bitcoin ₩1,800 trillion → bitcoin dominance = 1,800 ÷ 3,000 = 60.00%, altcoins' share 40.00%
Bitcoin unchanged while altcoins grow from ₩1,200 trillion to ₩1,500 trillion → dominance = 1,800 ÷ 3,300 = 54.55%
Over the last 90 days bitcoin +10%, and 40 of the top 50 altcoins rose more → 40 ÷ 50 = 80% → 75% or more, so it meets the index's "altcoin season" rule
Bitcoin -10% while Coin A falls -25% → ₩10,000,000 (about $7,100) in each becomes ₩9,000,000 in bitcoin and ₩7,500,000 in Coin A
Premiums at the same moment: bitcoin +1.00%, ether +1.20%, Coin B with deposits closed +18.00% → beyond ±15%, so CoinGaja's tables hide Coin B's premium
※ Example numbers, for illustration only
See it on CoinGaja
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