TikTok owner ByteDance on Wednesday lost its court challenge against its designation as a gatekeeper under landmark EU tech rules, in a boost for EU antitrust regulators seeking to rein in the power of Big Tech.

Under the Digital Markets Act (DMA), gatekeepers are required to make their messaging apps interoperate with rivals, let users decide which apps to pre-install on their devices and are not allowed to favour their own services over rivals.

ByteDance had argued that its designation risks undermining the DMA goal by protecting dominant companies from newer competitors such as TikTok, which does not have an entrenched position.

The Luxembourg-based General Court sided with the European Commission and dismissed its challenge, saying that ByteDance had not sufficiently substantiated its arguments.

(For top technology news of the day, subscribe to our tech newsletter Today’s Cache)

"The Commission was fully entitled to consider that Bytedance was a gatekeeper," judges said.

They said the company met the DMA's quantitative thresholds, regarding its global market value, the number of TikTok users within the European Union and the number of years during which that threshold relating to user numbers had been met.

The Court also pointed to TikTok's sharp jump in popularity to put it on par with rivals Meta Platforms and Alphabet.

"It had rapidly consolidated its position, and even strengthened that position over the following years, despite the launch of competing services such as Reels and Shorts, to the point of reaching, in a short time, half the size, in terms of number of users within the European Union, of Facebook and of Instagram," judges said.