• Etsy and eBay reported first-quarter results after the bell on Wednesday.
• Both of the companies gave disappointing guidance for the current quarter, sending their stocks sharply lower in extended trading.
• The weak second-quarter guidance suggests a cooldown in the e-commerce sector after a pandemic-fueled boost in online shopping.

Etsy and eBay reported better-than-expected first-quarter results after the bell on Wednesday, but the companies gave weak guidance for the current quarter that suggests the e-commerce sector is cooling off after a pandemic-fueled boost.

Shares of eBay fell more than 6% in extended trading, while Etsy's stock plunged as much as 12%.

Here's how Etsy did, compared with expectations of analysts surveyed by Refinitiv:

• Earnings per share: 60 cents vs. 60 cents expected
• Revenue: $579 million vs. $575 million

And here's how eBay did, compared with expectations of analysts surveyed by Refinitiv:

• Earnings per share: $1.05, adjusted, vs. $1.03 expected
• Revenue: $2.48 billion vs. $2.46 billion

Etsy and eBay are contending with rising concerns that e-commerce companies won't be able to sustain the high-flying growth they enjoyed during the coronavirus pandemic. During the pandemic, e-commerce companies across the board picked up business, which benefited their growth rates and lifted their stock prices.

After two years of outsized growth, investors have been gearing up for a slowdown, especially as the economy continues to reopen and consumers return to stores.

Even Amazon, which saw its business expand at a breakneck pace during the pandemic, hasn't been immune to the e-commerce reset. The company last week warned it could see its third-straight quarter of single-digit revenue growth, with revenue expected to grow between 3% and 7% in the current period.

Etsy saw its sales rise only 5.2% from a year ago, marking the first time revenue grew in the single digits. Revenue at eBay fell 17.9% year-over-year to $2.48 billion.

Etsy said it expects second-quarter revenue to come in between $540 million and $590 million, which is below the $628 million forecast by analysts, according to StreetAccount. Gross merchandise sales during the quarter are projected to be in the range of $2.9 billion and $3.2 billion, while analysts forecast GMS of $3.4 billion, according to StreetAccount.

Etsy CEO Josh Silverman blamed the guidance on tough pandemic era comparisons, but said he remains optimistic in the business' potential for sustained growth over the long term.

"We are emerging from an unprecedented time — and within that Etsy had unprecedented growth," Silverman said in a statement. "In a world of so many more choices, our guidance implies somewhere between a decline of low to high single digits for Etsy marketplace GMS year-over-year — retaining over 90% of the gains we have made over the past 2 years. Despite the near-term uncertainty, we have ample reason to remain very optimistic for the long-term."

Etsy CFO Rachel Glaser said on the analyst call that the company began to witness a deceleration in GMS in February and it "worsened throughout the quarter." She pointed to rising inflation, the economic reopening and the war in Ukraine as catalysts behind the slowdown.

"To be sure, it's been a bit of an unpredictable and volatile start to the year," Glaser added.

Silverman downplayed the impact of a seller strike last month, during which thousands of sellers put their digital shops in "vacation mode" to protest a recent fee hike. He said on the call that less than 1% of Etsy sellers temporarily shuttered their shops and the company "saw no material impact to churn" rates on the platform.

EBay projected second-quarter revenue to come in between $2.35 billion and $2.4 billion, implying a slowdown of 9% to 7% year over year. Wall Street projected second-quarter revenue of $2.54 billion, according to StreetAccount.

The company also gave a weak earnings forecast for the current quarter. It said it expects 87 cents to 91 cents in adjusted earnings per share, while analysts had expected $1.01 per share, according to StreetAccount.

Watch CNBC's full interview with Etsy CEO Josh Silverman