Eilish, 22, said later that she had not meant to single out any artist and added that she had participated in the practice, too. (Both artists’ work remains available in a variety of physical formats, though Eilish has stressed sustainability.)

Still, when Swift pre-empted the release of Eilish’s album last week with three special digital editions of “Tortured Poets,” available for 24 hours and including previously unheard “first-draft phone memo” demos, many saw the move as pointed. Especially online, where pop fan allegiance can be a blood sport, the matchup became one to watch.

Eilish soon released her own new digital edition of “Hit Me Hard and Soft,” which added isolated vocal tracks for each song. Such maneuvers — in which listeners invested in the chart success of their favorites are incentivized to stream and buy more with bonus content — are popular and common, especially amid close contests for bragging rights, in the chess game that is the modern music business. But it didn’t end there.

On Tuesday, Swift released a remix of her hit “Fortnight”; on Wednesday, Eilish posted a new remix of “L’Amour De Ma Vie.” And on Thursday, the final day of Billboard’s tracking week, Eilish expanded her album again, releasing limited edition versions of each song both slowed down and sped up. (Eilish’s labels, Darkroom/Interscope, also discounted “Hit Me Hard and Soft” to $4.99 as an iTunes download — a more popular chart-minded move in an earlier era of digital sales — while Swift’s “Tortured Poets” remained at $14.99. Swift’s “Fortnight” remix was priced at 69 cents, less than the typical single price of 99 cents or $1.29.)

Midweek predictions, which predated some of the latest bonus releases, gave Swift the slight edge, with an estimated 350,000 equivalent units to Eilish’s 300,000, according to Hits magazine, whose totals sometimes vary from the official count. (Eilish’s previous album, “Happier Than Ever,” sold 238,000 in its first week, slightly less than the 313,000 units her debut sold in 2019.)