Microsoft added $135 billion on its Copilot relaunch, 41% of the S&P 500's gain. The rest of software fell.

Microsoft rose 3.66% on Friday, 25 September, and added $135.4 billion in market value, about 41% of the S&P 500's $333.5 billion gain for the day. The index closed up 0.47%. Take Microsoft out and the other 499 companies rose 0.30% between them.

The move came on the day Microsoft released a redesigned Copilot. The same session also brought the index's largest dollar loss: Meta gave back $66.1 billion.

The gain was concentrated

Coming into Friday, Microsoft was 5.25% of the S&P 500 by market value. It supplied nearly eight times that share of the day's gain. Two stocks did most of the work:

Microsoft and Apple together account for $210.6 billion, 63% of the index's gain. The rest of the market was positive too: 327 companies rose and 171 fell. Industrials were the best sector, up 0.96% cap-weighted. Energy was the worst, down 0.88%, with only 5 of its 21 stocks higher.

On the site's map, Technology rose 0.69% and added $198.0 billion. Without Microsoft, the sector rose 0.25% and added $62.5 billion.

What Microsoft announced

According to 24/7 Wall St., Microsoft combined its consumer and workplace Copilot assistants into one app built for businesses. The app has three parts: a home hub for chat and handing off tasks, a coding tool built on GitHub Copilot, and Autopilot, a persistent agent that runs longer tasks in the background. The same report says everyday chat will be sold at a fixed subscription rate and agent work will be billed pay-as-you-go. It also says Oppenheimer raised its price target on the stock to $570 from $515 that morning.

The Motley Fool reported that 37.9 million Microsoft shares traded on Friday, about 15% above the three-month average.

How unusual the day was for Microsoft

Microsoft closed at $516.17. The site's daily price history puts that in context:

• The highest close of 2026. The previous high for the year was $513.53.
• The highest close since 3 November 2025, when the stock closed at $517.03.
• The biggest one-day gain since 3 August, when it rose 4.93%.
• 46% above its 2026 low, a close of $352.83 on 25 June.

The rest of software fell

The larger enterprise-software and IT-services companies on the map mostly moved the other way on Friday:

Together those nine lost $24.1 billion. Microsoft gained more than five times that. The group did not fall uniformly: $DDOG Datadog rose 4.36% and $CDNS Cadence rose 1.28%. None of the reports we cite ties the declines to Microsoft's announcement, and these figures cover a single day. They show the direction and size of the split, not its cause.

Meta went the other way

Meta fell 3.33% and lost $66.1 billion, the largest dollar loss in the index on Friday. Meta took about 0.09 percentage points off the S&P 500's return while Microsoft added about 0.19. Without both of them, the index rose 0.41%.

This was Meta's worst day since 18 August, when it fell 4.45%. It followed a run that 24/7 Wall St. put at 32% over the past month, which included an 11.34% jump on 21 September as its Muse AI agent drew attention, and a further 4.50% on Thursday. After Friday's drop, Meta still closed at $751.66. That is 12.9% above its 18 September close of $665.75, the session before that jump.

24/7 Wall St. called Friday's move profit-taking. It pointed to Meta's 2026 capital spending guidance of $130 billion to $145 billion, compared with second-quarter free cash flow of $784 million, and said the next quarterly report, with the first revenue detail on Muse, could be the next test for the stock.

The whole map

The treemap at the top of this post shows the full 25 September session: every S&P 500 company sized by market value and coloured by its move. The day's recap, linked below the map, has the sector-by-sector breakdown.

StockTreeMap describes what happened in the market and does not give investment advice.