That includes 10,000 seasonal workers for its distribution centers and 3,000 to help stores cater to cross-channel shoppers.
The retailers led Internet Explorer and Firefox consistency tests, respectively.
Overstock.com had the best consistency score in Internet Explorer testing among large retailers measured in January, says application performance management firm Compuware Gomez. Last month, the retailer had the most consistent Internet Explorer site loading time with a variation of 0.63 seconds. Apple.com had the best Firefox consistency score at 0.49 seconds.
Dell.com (0.86 seconds) placed second in Internet Explorer tests. Apple.com (0.90) came in third, Costco.com finished fourth (0.92) and Walmart.com (1.16) in fifth.
In Firefox testing, LLBean.com came in second place behind Apple.com with a variation in web page delivery of 0.65 seconds. Costco.com placed third (0.73), followed by Overstock.com (0.93) and Macys.com (0.96).
The average Internet Explorer consistency score among the 22 retailers measured in January was 1.78 seconds. The same group of retailers produced an average Firefox score of 2.03 seconds.
The consistency ratings take into account differences in the speed of web page delivery across multiple visits.
Click here for the full test results.