Reconciliations of the non-GAAP metrics to the nearest GAAP metrics are included in ZipRecruiter's public S-1 filing and in our Form 10-Q.
GDP growth exceeded 6%.
According to July's jobs report released on August 6, 2021, we've now recovered almost 75% of the jobs lost during the pandemic.
We responded to the increased demand from employers by scaling up our sales and marketing efforts, resulting in nearly 170,000 quarterly paid employers participating in our marketplace, an all-time high.
Revenue of $183 million this quarter was also the highest in ZipRecruiter's history.
Specifically, we grew headcount in the second quarter by 140, which is a record high for our company.
We now have over 1,000 ZipRecruiter employees.
As Ian mentioned, our second-quarter revenue of $183 million represented a record quarter, exceeding the midpoint of our guidance range by $23 million.
This represents a 109% growth year over year and 46% growth over the first quarter of 2021.
At almost 170,000, this represented an improvement of 120% year over year, an another all-time high for ZipRecruiter.
GAAP net loss was $53 million in the second quarter of 2021 compared to net income of $21 million in the prior year.
Adjusted EBITDA loss was $2 million with a negative 1% margin compared to $26 million in adjusted EBITDA or a 29% margin in the prior year.
In the second quarter of 2021, we incurred $64 million in stock-based compensation expense, $42 million of which related to the modification and expense of employee RSUs to allow for vesting in the direct listing, which impacted net loss.
Similarly, in the second quarter of 2021, we incurred $32 million in general and administrative expenses related to the direct listing completed during the quarter, which impacted both net loss and adjusted EBITDA loss.
Even with the investments discussed earlier and onetime expenses for our direct listing, we ended the quarter with over $153 million in cash, an increase of $18 million from the first quarter of 2021.
Additionally, we secured a $250 million line of credit, none of which was drawn as of the quarter end.
Following the largest increase in quarterly revenue in ZipRecruiter's history, we expect $185 million of revenue in Q3 of 2021 at the midpoint, which translates to 80% year-over-year growth.
We're pleased to increase our midpoint guidance for the full year to $658 million, up from the $590 million shared last quarter.
This increased 2021 revenue guidance equates to 57% growth over 2020 at the midpoint.
Our full-year midpoint guidance for adjusted EBITDA of $34 million equates to an adjusted EBITDA margin of 5%.
This is above our pre-COVID adjusted EBITDA margin of 2% back in 2019 despite our investments to achieve substantially higher growth rate this year.

Summary:
Revenue of $183 million this quarter was also the highest in ZipRecruiter's history.
As Ian mentioned, our second-quarter revenue of $183 million represented a record quarter, exceeding the midpoint of our guidance range by $23 million.