For years, Ben Black’s telephone irritated his household. It was the one Android machine in a household message group with eight iPhones. Due to him, movies and pictures would arrive in low decision and there could be inexperienced bubbles of textual content amid bubbles of blue.

However a brand new app known as Beeper Mini gave him the power to alter that.

Mr. Black, 25, used the app to create an account for Apple’s messaging service, iMessage, together with his Google Pixel telephone quantity. For the primary time, each message the household exchanged had a blue bubble and members had been in a position to make use of perks like emojis and animations.

Because it was launched on Dec. 5, Beeper Mini has rapidly change into a headache and potential antitrust drawback for Apple. It has poked a gap in Apple’s messaging system, whereas critics say it has demonstrated how Apple bullies potential rivals.

Apple was caught unexpectedly when Beeper Mini gave Android units entry to its trendy, iPhone-only service. Lower than per week after Beeper Mini’s launch, Apple blocked the app by altering its iMessage system. It mentioned the app created a safety and privateness danger.

Apple’s response set off a sport of Whac-a-Mole, with Beeper Mini discovering alternative routes to function and Apple discovering new methods to dam the app in response.

The duel has raised questions in Washington about whether or not Apple has used its market dominance over iMessage to dam competitors and drive customers to spend extra on iPhones than lower-priced options.

The Justice Division has taken curiosity within the case. Beeper Mini met with the division’s antitrust attorneys on Dec. 12, two folks acquainted with the assembly mentioned. Eric Migicovsky, a co-founder of the app’s guardian firm, Beeper, declined to touch upon the assembly, however the division is in the midst of a four-year-old investigation into Apple’s anticompetitive habits.

The Federal Commerce Fee mentioned in a weblog submit on Thursday that it could scrutinize “dominant” gamers that “use privateness and safety as a justification to disallow interoperability” between providers. The submit didn’t title any corporations.

The battle additionally caught the eye of the Senate Judiciary subcommittee on antitrust. The committee’s management — Senators Amy Klobuchar, Democrat of Minnesota, and Mike Lee, Republican of Utah — wrote a letter to the Justice Division expressing concern that Apple was snuffing out competitors.

Apple declined to touch upon the letter.

The questions coming from Washington minimize to the guts of at present’s smartphone competitors. Rival smartphone makers credit score iMessage with serving to Apple broaden its smartphone market share in the USA to greater than 50 p.c of smartphones offered, up from 41 p.c in 2018, in accordance with Counterpoint Analysis, a expertise agency.

Messaging has been a key a part of Apple’s technique to promote extra iPhones. For years, it has made exchanges between iPhones and Android units as primary because the texts between decades-old flip telephones. Texts between iPhone customers seem in blue and could be tapped to provide a thumbs up, however texts with Android customers seem in inexperienced and haven’t any easy perks.

Android corporations have tried to struggle again. An Android smartphone maker, Nothing, has collaborated with an app known as Sunbird to supply iMessage. Google, which has developed the Android working system, has pressured Apple to undertake a expertise known as wealthy communication providers, which might make it attainable to ship high-resolution video and pictures between competing smartphones.

However their efforts haven’t made a lot of a dent. Final month, Apple mentioned it could undertake the expertise within the coming yr. The transfer means Android customers will get pleasure from advantages like sharing higher-resolution movies however be caught with the inexperienced bubbles for textual content messages, which have change into stigmatized and related to much less wealth.

“Everyone seems to be watching to see what sort of response Apple goes to need to Beeper Mini,” mentioned Cory Doctorow, a particular adviser to the digital rights advocacy group Digital Frontier Basis who has written a e book about interoperability throughout completely different applied sciences. “We will’t inform how frightened they’re internally, however their response might have a huge effect on how messaging works.”

Defending iMessage is a decade-old technique at Apple. In 2013, Craig Federighi, Apple’s head of software program, opposed making iMessage workable on rivals’ units as a result of it could “take away an impediment to iPhone households giving their children Android telephones,” in accordance with emails launched through the firm’s courtroom struggle with Epic Video games, the maker of Fortnite.

Tim Prepare dinner, Apple’s chief government, has resisted calls to alter that place. He instructed an iPhone proprietor at a convention final yr that the answer to inexperienced textual content messages was to purchase iPhones for family and friends members.

Beeper introduced a special method to messaging. Mr. Migicovsky created the corporate in 2020 to construct a single messaging app that might ship texts throughout a number of providers, together with WhatsApp and Sign.

Mr. Migicovsky managed to combine most messaging providers, besides iMessage. In contrast to its friends, Apple didn’t supply an online app, making it tough to attach with its service. The one means Beeper might combine iMessage was to route messages by means of Mac computer systems after which to an iPhone. The method delayed messages and made them much less safe.

As Beeper struggled with iMessage, an adolescent in Bethlehem, Pa., discovered another answer. James Gill, a 16-year-old laptop hobbyist, made it his private objective to determine how iMessage labored. He used software program to decrypt his iMessages and decided that Apple used its push notification system — the identical one which delivers information alerts — to ferry messages between units.

“It wasn’t genius perception,” mentioned Mr. Gill, a junior at Saucon Valley Excessive Faculty. “I used to be simply poking at it for a very long time.”

In June, Mr. Gill revealed his findings on GitHub, a software program platform the place programmers share code. When Mr. Migicovsky noticed the submit, he thought it might assist Beeper clear up its iMessage drawback. He supplied Mr. Gill a job making $100 an hour, a significant enhance from the $11 an hour the excessive schooler was making as a cashier at McDonald’s.

The job has been extra concerned than Mr. Migicovsky or Mr. Gill anticipated. Since Beeper Mini’s launch this month, Apple has modified iMessage about thrice, Mr. Migicovsky mentioned.

Every change by Apple required an adjustment by Beeper. Its newest answer includes routing registration data to Beeper Mini customers by means of their private Mac computer systems.

“To dam it completely, they’ll need to provide you with a method to require an iPhone serial quantity,” Mr. Gill mentioned. “Beeper will nonetheless provide you with a workaround.”

An Apple spokeswoman mentioned it could proceed to replace iMessage as a result of it couldn’t confirm that Beeper stored its messages encrypted. “These strategies posed vital dangers to person safety and privateness, together with the potential for metadata publicity and enabling undesirable messages, spam, and phishing assaults,” she mentioned in an announcement.

Mr. Migicovsky disagrees. As an alternative of permitting Android clients to ship encrypted messages to iPhone clients, he mentioned, Apple is attempting to drive them to alternate unencrypted textual content messages. He has posted Beeper’s software program code on the net and inspired Apple and cybersecurity consultants to evaluate it.

Matthew Inexperienced, an affiliate professor of laptop science at Johns Hopkins College, mentioned Apple had some respectable safety considerations and warned that an prolonged struggle between the 2 corporations might doubtlessly introduce vulnerabilities that criminals might exploit.

“A world the place Apple works with third-party shoppers in a supported means is an effective one,” Mr. Inexperienced mentioned. “A world the place Beeper and Apple attempt to struggle one another in a tit-for-tat arms race is a foul one.”

In an try to finish the standoff, Mr. Migicovsky mentioned, he emailed Mr. Prepare dinner, however Apple’s chief has not responded.

“This wasn’t our intention,” Mr. Migicovsky mentioned. “We’re attempting to make it work, inside our management, for the great of the chat world.”