The index provider announced the change on 13 August, in a release issued at 18:12 in New York.
Reddit enters under the Communication Services sector. It trades on the New York Stock Exchange as RDDT.
A second change follows two days later. Sun Communities replaces Webster Financial in the S&P MidCap 400 on 20 August.
The seat opened because a landlord got bought
This is an off-cycle change, and the reason matters. Equity Residential is acquiring AvalonBay Communities, and the deal is expected to complete soon.
The combined company will be renamed Vivmark Residential and will keep its place in the index. So one S&P 500 constituent absorbed another, and the vacancy went to Reddit.
Webster Financial leaves the MidCap 400 for the same kind of reason. Banco Santander is acquiring it.
Reddit did not grow into a slot that was waiting for it. Two mergers created the openings, and the index provider filled them.
Why the shares moved
Reddit rose about 11% in extended trading on Thursday, CNBC reported. The stock had closed at $158.12.
The mechanism is passive money rather than enthusiasm. Fund managers who track the benchmark have to buy the shares to match the index.
That also changes who owns Reddit. Every European pension fund and retail investor holding an S&P 500 tracker will own a slice of it from Tuesday, whether or not anyone chose it.
Reddit becomes only the second pureplay social media company in the index. Meta is the other.
Pinterest and Snap both listed years earlier and are smaller by market capitalisation. Twitter sat in the index until Elon Musk bought it in 2022, and it is now X, owned by SpaceX.
The number that complicates the story
Reddit shares were down 31% for the year through Thursday’s close, Bloomberg reported. That is the context the announcement lands in.
The business is not the problem. Reddit posted its eighth consecutive quarter of revenue growth above 60% in July.
The desk covered that quarter, and the reaction to it. Revenue reached $805m, up 61%, profit more than doubled and daily active users climbed 18%, and the stock fell 20% anyway.
What spooked investors was a phrase. Reddit told them search referrals had been “choppy”.
Steve Huffman put the volatility down to Google pushing its Gemini-powered AI Overviews. His line on it was that Reddit is still looking for the win-win.
What it takes to qualify
The bar is public and specific. A company needs a market capitalisation of at least $22.7bn under the July guidelines, plus profitability, liquidity and share-float requirements.
Profitability is the part people forget. Plenty of larger technology companies fail that test, and Reddit only reached consistent profit recently.
The growth of passive investing has made inclusion matter more than it once did. A seat in the benchmark is now a permanent source of demand rather than a badge.
June brought the last comparable additions. Marvell Technology and Flex joined the index, replacing Pool Corp and Campbell’s.
Reddit listed in March 2024 and raised $748m in a top-priced flotation. Reaching the benchmark inside 30 months is quick by the standards of recent technology listings.
Reddit’s own framing
The company put out its own release on Friday morning. It calls the model a one-of-one combination of growth with best-in-class profit and cash flow margins.
Drew Vollero, the chief financial officer, supplied the quote. “Reddit’s raw materials are special, and there is so much potential to continue building great products and scaling profitably,” he said.
The release leans on the corpus rather than the audience. Reddit puts it at more than 26 billion posts and comments, with more than 130 million daily active uniques.
It also calls itself an ever-growing record of human experience across nearly every topic. The phrasing points at buyers of training data as much as at buyers of advertising.
That framing is deliberate. Reddit is describing itself to investors as a data asset in an AI economy, not as a website with visitors.
The AI deals investors wanted more of
Reddit has signed agreements worth hundreds of millions with OpenAI and Google, both of which train on its data. Bloomberg reports that investors had hoped for more of them.
The Google arrangement is the one under pressure. Signed in 2024 at roughly $60m a year, it is up for renewal, and Reddit wants pricing tied to usage rather than a flat fee.
That puts Reddit on the same side of an argument Apple is having with news publishers. Both fights are about whether AI content licensing pays a guaranteed sum or a metered one.
The infrastructure is moving the same way. Cloudflare has set a September deadline for AI crawlers to pay publishers or face blocking by default.
The difference is which end of the deal each party sits on. Reddit wants the meter because it thinks it is being underpaid, and Apple wants the meter because it does not want to pay a floor.
Google is the dependency and the customer
The awkward part of Reddit’s position is that one company occupies three roles. Google sends much of its traffic, pays to train on its data, and runs the product eating its referrals.
The desk has covered AI Overviews cutting publisher clicks by 58 per cent before Google began adding features to send some back.
Reddit sits inside that trend and slightly outside it. Its content is what the summaries are often summarising, which is also why the licensing cheques exist.
There is a related pressure on the corpus itself. Brands have been planting fake posts to be picked up by chatbots, and Reddit is now fighting that marketing slop with its own systems.
What would settle it
Three things, and the first is Tuesday itself. Index additions often give up part of the initial jump once the tracker buying is done, so the price on 18 August tells you how much of this was mechanical.
The second is the Google renewal. A usage-based deal at a higher number would answer the complaint that drove the stock down.
The third is the referral line in the next quarter. If “choppy” becomes a trend rather than a quarter, index membership will not change what investors are worried about.
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