Tech stocks have risen so far and fast in the past year, that even as they recently shrugged off a record-fast dive into correction territory, many on the Street have been positing this may be another tech bubble, akin to 2000.

So, is that the case? Are we having stock bubble déjà vu?

To be sure, there are "myriad" ways tech stocks today resemble the bubble in 2000, analysts led by Toni Sacconaghi at firm AllianceBernstein wrote in a recent research note. But there are a few important differences, too.

Performance

For starters, the firm notes tech stocks have been "sustained" outperformers of the overall market for eight consecutive years. The top 12 mega tech names (think Apple, Microsoft, Tesla) have risen 170% on average in the past year, versus 146% in the year before the 2000 crash. The analysts also looked at the six months preceding the Dot Com crash and found stocks soared 83% in that time (for comparison, tech stocks were up 79% in the last six months, before the early September correction), showing similar run-ups in tech stock prices.

Weighting

Tech always carries a heavy weight, but that increases markedly when investors bid shares up. The top 10 tech stocks make up 29% of the S&P's total market cap (higher than 2000's 23%), analysts at the firm point out.

Retail investors

And, of course, the massive increase in retail investor activity spurred on by free trading platforms like Robinhood and fractional share ownership is elevated, "akin to what happened in 1998-2000," the analysts write, when "online trading proliferated." Now, analysts at the firm note "signs of mania associated with a bubble are also appearing," especially in high fliers like Apple and Tesla who both recently performed stock splits.

Yet there's one big difference between now and 2000 that has analysts at AllianceBernstein still recommending tech (as a market weight): Valuations now are actually not quite as extreme as in 2000.

In fact, analysts led by Sacconaghi note "the magnitude of the tech run-up and valuations today remain notably below 2000 bubble levels," as "tech appreciation was much more pronounced in the bubble." For one, the firm notes the tech-heavy Nasdaq appreciated 43% per year in the seven years before the 2000 tech bubble burst (and a whopping 288% in the final year), whereas the index has appreciated an average of 23% per year over the last seven years up until 2020, via compound annual growth rate (CAGR). Analysts at AllianceBernstein note that while "valuations are very elevated, [they are] nowhere near the levels of the peak of the bubble."

The firm's analysis shows that, on an absolute basis, tech stocks in 2000 were trading at 45.8 times forward price-to-earnings in March 2000, whereas tech in September 2020 is trading at roughly 26.9 times forward earnings (equal weighted), as of Aug. 31. Meanwhile, the cap weighted tech index traded at 53 times forward earnings back in March 2000 compared to 34 times forward earnings today, while price-to-free cash flow valuations were "even more extreme," the firm notes, at 118 times in 2000 versus 31 times today.

One reason for that is unlike in 2000, "these companies actually have revenues and earnings, they're not just trading on fumes or expectations," CFRA Research's Sam Stovall tells Fortune. In that sense, comparing 2000 to 2020 isn't "apples to apples," he says.

But just because valuations aren't as heady based on some measures as in 2000 doesn't mean analysts think tech is a steal by any means.

"Tech stocks are still trading at their highest levels since the bubble and we note that tech sector earnings growth is expected to significantly lag the broader market in 2021—meaning valuations based on 2021 earnings are considerably higher for tech on a relative basis," analysts at AllianceBernstein wrote.

And with tech stocks having seen a torrid run-up, their current supremacy may be on shaky ground—especially if earnings in tech prove lackluster, beckoning investors back to those cyclical and value stocks that have lagged this year.

Yet in light of the expectations that work from home and tech-dependent trends won't be disappearing anytime soon (not to mention the Don't Fight the Fed argument), it appears tech bulls are continuing to stand their ground.