Over the last year, state legislators concerned about a mental health crisis among the nation’s young people have passed a raft of children’s online safety measures. A new Utah law would require social networks to obtain a parent’s consent before giving an account to a child younger than 18 while a new California law would require many sites to turn on the highest privacy settings for minors.

Now Louisiana lawmakers have passed an even broader bill that could affect access to large swaths of the internet for minors in the state.

The Louisiana measure would prohibit online services — including social networks, multiplayer games and video-sharing apps — from allowing people under 18 to sign up for accounts without parental consent. It would also allow Louisiana parents to cancel the terms-of-service contracts that their children signed for existing accounts on popular services like TikTok, Instagram, YouTube, Fornite and Roblox.

The Louisiana civil code already allows parents to rescind contracts signed by unemancipated minors. Laurie Schlegel, the Republican state legislator who spearheaded the new measure, said her bill simply made it clear that the state’s existing contracting rules also covered accounts on online content-sharing platforms.

“This is already the law in Louisiana,” Ms. Schlegel said in an email, noting that young people lacked the capacity to understand and agree to the slew of contract terms that online services often require to open an account. “We are just making it clear to some irresponsible online companies who are contracting with minors without parental consent.”

On Tuesday, the Louisiana State Legislature passed the bill by a unanimous vote of 97 to 0. The State Senate had already passed the measure. The bill now requires approval by Gov. John Bel Edwards, who has not taken a public stance on the measure. If he signs the bill, it will take effect Aug. 1 of next year.

The state bill comes two weeks after the surgeon general issued a public advisory warning Americans that social media posed a serious risk to young people’s mental health and urging policymakers to limit access for children. It may be welcomed by many parents worried that their children are being inundated with inappropriate content or spending unhealthy amounts of time online.

TechNet, an industry group whose members include Meta, Snap, Google, Amazon, Apple and Uber, opposed the bill, saying it was overly broad and could cause friction for all users, including adults.

“The bill will require all users to provide proof of their age in order to comply with the law and ask parents to provide proof that they are the minor’s parent in order to access the platform,” Servando Esparza, TechNet’s executive director for Texas and the Southeast, said in an emailed statement. “This could jeopardize privacy and lead to unintended consequences,” he added, noting that Louisiana legislators had recently amended the bill to require research on its potential impact before the measure would take effect.

The Louisiana online contracts bill is part of a new wave of state laws this year regulating internet services that could pose risks to young people. And it underscores an escalating effort among Republican state legislators to give families more control over their children’s online activities.

Last year, Ms. Schlegel spearheaded the passage of a Louisiana law that requires sexually explicit sites to verify that users in the state are 18 or older by checking credentials like a verified digital driver’s license. The law took effect in January.

Since then, at least five states — Arkansas, Mississippi, Montana,Utah and Virginia — have passed similar age-verification laws for pornography sites.

In March, Republican lawmakers in Utah initiated the passage of a restrictive social media bill that would require social networks to verify a user’s age and obtain parental consent for minors to have accounts. The legislation also gives parents access to their child’s online posts and messages. Arkansas enacted a similar measure in April.

In May, the Free Speech Coalition, a group representing adult entertainment sites, sued Utah to try to block the pornography age-verification bill on free speech grounds, saying it violated Americans’ rights to view constitutionally protected information.

Civil liberties groups have raised similar concerns about broader child online safety bills, saying the measures could hinder young people from viewing online information.

The new Louisiana bill does not specifically require social media, multiplayer game and other sites and apps to verify the ages of users in the state. And it does not include specific penalties for companies that fail to comply.

Even so, it may cause some online services that currently ask new users to volunteer their birth dates to institute more stringent age-verification and parental-consent procedures.

Like Ms. Schlegel’s pornography bill, the new online contracting bill could also be widely copied. Civil codes in many other states have similar rules regarding contracts with minors.

“It is time for big tech to be more responsible to our children online,” Ms. Schlegel wrote. “The harm is real.”