On YouTube, though, the duo were beaten by Lil Nas X's Old Town Road, while Shazam's chart was topped by Shawn Mendes and Camila Cabello's Señorita.
For a decisive verdict, we need the Official Charts Company - who combine sales and streaming figures to come up with a definitive placings for summer's biggest songs.
...Justin and Ed's I Don't Care, which came out on top with the equivalent of 755,000 sales, made up of 90 million streams and 115,000 downloads.
Like the best summer songs, it doesn't take itself too seriously - the video sees the two A-listers dressing up as ice creams and bananas as they sing about escaping a boring party with their girlfriends.
Musically, the song is built around the Tresillo, or Dembow, rhythm - a syncopated beat that's become a mainstay of summer songs, from Luis Fonsi's Despacito to Sheeran's own Shape of You.
Originating in Africa, the boom-ti-boom-chk rhythm made its way to Cuba in the 19th Century, where it became the basis for Habenera music.
After ricocheting around the Caribbean, the beat was co-opted into reggaeton, which has, in turn, inspired dozens of pop hits, thanks to its ability to evoke end-of-term excitement and long, hazy days in the sun.
On Spotify's global chart, where Latin music has a major presence, Tresillo underpins six of the summer's most-streamed songs, including Bad Bunny's Callaita and Daddy Yankee's Con Calma.
Lewis Capaldi's Someone You Loved soundtracked enough break-ups to become the UK's third most popular song of July and August (the singer's equally sorrowful Hold Me While You Wait came eighth, which tells you something about the fate of summer romances).
Billie Eilish's Bad Guy, on the other hand, couldn't be more moody, but crept into the top five by the simple trick of sounding like nothing else on the radio.
The same could be said for Lil Nas X, whose attempt to pull off a country-rap crossover was more successful than anyone could have imagined.
His breakout track Old Town Road, which topped the US charts for a record-breaking 19 weeks, was the UK's second-biggest song of the summer, scoring 723,000 chart sales.
It was also the UK's most-streamed video, topping the YouTube chart thanks to a hilarious, self-aware mini-movie that amassed 41.5 million views over the last two months.
Shawn Mendes and Camila Cabello's steamy duet Señorita also fared well on YouTube - amassing 23 million views to become the summer's second most-watched music video.
That, combined with the song's popularity on Shazam (which allows users to tag songs on their phone and add them to their music library), suggests it could have become the overall song of the summer, had it been released earlier in the year.
1500w Fog Machine With Led
Follow us on Facebook, or on Twitter @BBCNewsEnts. If you have a story suggestion email firstname.lastname@example.org.
Uefa urges the "football family" to "wage war on the racists" after the abuse of England players in Bulgaria.
Project Truss, Performance Truss, Corner For Truss, Circular Truss - Reichy,https://www.chinastagetruss.com/