Bitcoin is showing strength again, but something interesting is happening underneath the surface.

Altcoins are starting to move too.

On September 18, Bitcoin climbed nearly 6% in 24 hours, but several major altcoins moved even faster. Ethereum gained around 7%, XRP almost 9%, while Solana jumped more than 12%.

That difference matters.

Crypto rallies often begin with Bitcoin attracting most of the attention and liquidity. If confidence improves, activity can gradually spread toward Ethereum, large-cap altcoins and eventually smaller projects.

We may be seeing the early signs of that process now.

Bitcoin dominance — BTC's share of the total crypto market — has already shown periods of decline this month. Earlier in September, it dropped for five consecutive trading days from about 60.4% to 59.35%.

When Bitcoin remains relatively strong while its dominance falls, it can indicate that other cryptocurrencies are growing faster than BTC.

But that doesn't automatically mean altseason has arrived.

The latest moves could simply be a broad market rebound rather than a sustained rotation away from Bitcoin. Recent market data still shows Bitcoin representing roughly 60% of the crypto market, so BTC remains the dominant force.

There is also a big difference between a few altcoins pumping and the entire altcoin market becoming strong.

Solana provides a good example.

SOL recently surged above $112 to a seven-month high, outperforming Bitcoin. Tokens within the Solana ecosystem, including JUP, RAY and MET, also posted strong gains during the move.

XRP has also attracted renewed attention as focus has started shifting toward major altcoins.

This tells us that traders are becoming more willing to take risk outside Bitcoin.

But there is still one major obstacle: the macro environment.

CoinShares noted on September 18 that tighter monetary conditions and a more hawkish Federal Reserve remain headwinds for the broader crypto market. Its analysis suggested that these conditions could put even greater pressure on altcoins than on Bitcoin.

So this market may still need confirmation.

If Bitcoin stays strong while dominance continues falling and more altcoins begin outperforming BTC, the case for broader capital rotation would become stronger.

If Bitcoin dominance starts climbing again, however, the recent altcoin strength may turn out to be selective rather than the beginning of a full market-wide altseason.

For now, the interesting part isn't simply that altcoins are green.

It's that some of them are beginning to move faster than Bitcoin.

And if that trend spreads across more of the market, capital rotation could become one of the biggest crypto stories to watch next.