The list is based on the input of employees who provide anonymous feedback about their job, work environment and employer on a five-point scale.
Software company Salesforce is this year’s winner with a rating of 4.5, followed by Microsoft at 4.4 and web-based business Abcam with 4.4.
Google, Softcat, GTB, Apple, Bella Italia, SAP and Facebook took the other top 10 positions in the list.
Salesforce was named overall UK winner for its ‘Ohana’ family culture, commitment to diversity and inclusion, strong range of benefits and perks and a strong CEO.
It was the only company to appear on all five country lists, the others in France, Germany, the US and Canada.
Despite the huge pressures placed on the hospitality sector due to coronavirus restrictions, four restaurants made it to the top 50: Bella Italia, Nando’s, Wagamama and Greggs.
Bella Italia rose from 45th in 2020 to eighth thanks to its fun and friendly teams, family feel and good pay, tips and discounts. This is despite having to make redundancies last year.
Other high-scoring sectors included finance and manufacturing.
Christian Sutherland-Wong, Glassdoor CEO, said coronavirus naturally had a large impact on this year’s list.
He said: “COVID-19 is in the driver’s seat and every employer has been impacted. This year’s winning employers have proven, according to employees, that even during extraordinary times, they’ll rise to the challenge to support their people.
“A mission-driven culture, transparent leadership and career opportunities are always hallmarks of Best Places to Work winners. This year, we also see exceptional employers who have prioritised the health, safety and wellbeing of their employees.”
The largest falls in 2021’s list were Cisco Systems, from 13 to 44, Shell from 20 to 50 and GlaxoSmithKline, which was down to 46 from 29.
2020 winners no longer on the list included Hiscox, Topps Tiles, easyJet, Nike, O2, Rolls Royce and Unilever.
Half of the 50 companies are headquartered in the UK, of which nine are in London, three in Cambridge, three in Slough and two in Birmingham.
None are based in Scotland, Wales or Northern Ireland.
Each company must have at least a 3.5 overall company rating, and at least a 2.5 across workplace factor ratings such as career opportunities, compensation and benefits, culture and values, senior management and work-life balance during the eligibility period.
Among the 1.3 million employers reviewed on Glassdoor, the average company rating is 3.5.