Consumers worried about identity theft after last year’s massive Equifax data breach can finally freeze their credit reports at all three credit bureaus free of charge. However, each bureau is now offering credit lock tools, sometimes with hefty monthly costs, as alternatives to credit freezes.

Credit locks and freezes are similar. They both prevent others from accessing your credit information, eliminating the possibility that a fraudster could open a new credit account in your name. To entice consumers to use credit locks, the credit bureaus cite convenience and may offer special deals. Equifax, for instance, offers a new product called “Lock & Alert” free for life.

However, there are some important differences to keep in mind when deciding which tool to use. A credit freeze offers more stringent legal protections, making it the better option for consumers, according to Christina Tetreault, a staff attorney on the financial services team at Consumers Union, the advocacy division of Consumer Reports.

Here’s a look at the key differences between a credit lock and credit freeze.

A Credit Freeze Offers Stiffer Protections

Perhaps the main reason a security freeze is the better option is that its promise to guard your credit accounts is guaranteed by law, Tetreault says. By contrast, a credit lock is simply an agreement between you and the credit reporting agency.

“Having a contractual agreement is not as strong as having protections under law,” Tetreault says. “The contract may be unclear, may include provisions that allow the other party to change it, or include provisions that you may be better off not agreeing to, such as an arbitration agreement,” she says.

For example, immediately following the breach, Equifax introduced its free TrustedID Premier product, which lets consumers lock their credit and provides credit monitoring. But it also included an arbitration agreement requiring that any disputes be settled out of court, which would also prohibit consumers from participating in a class-action suit.

Following consumer outrage, however, the company said it would no longer enforce the arbitration clause. An Equifax spokesperson now says the arbitration clause has been removed from TrustedID's terms and conditions.

More on the Equifax Breach

Because security freezes are now covered by Federal law, if something goes wrong—for example, if credit accounts are fraudulently accessed anyway—consumers will be protected from any financial liability, says Chi Chi Wu, staff attorney focused on consumer credit issues at the National Consumer Law Center, an advocacy group.

“With locks, it’s not clear who would be liable” for any losses, she says.

Wu recommends that consumers freeze their credit rather than lock it, because the products are so new and there are still many unknowns, she says.

A Lock Can Be More Convenient

Credit locks may be less complicated and less time-consuming to manage than credit freezes.

All consumers requesting a freeze from Experian get a personal identification number to use to manage their credit information. Equifax and TransUnion have you create a password if you manage your credit online, and will issue you a PIN if you manage your credit on the phone or by mail.

These PINs and passwords are important because you’ll need them in case you want to temporarily lift your credit freeze in the future, for instance, if you want to apply for a new credit card. And remember, you’ll have to make the request with each of the credit bureaus.

“It’s important to keep [the PIN or passwords] somewhere safe,” Rossman says.

And it may take a bit of time before a request to lift a freeze goes into effect.

“The new law mandates that credit freezes can be lifted in less than 1 hour, but I recommend allowing a bit more lead time,” says industry analyst Ted Rossman. “For example, if you’re planning on car shopping soon, I’d lift the freeze about three business days before applying for an auto loan. That gives you a grace period in case you hit an unexpected delay.”

A credit lock, on the other hand, is activated or lifted using an app on your smartphone, and it’s instantaneous.

Cost Considerations

Convenience can be costly. Only two credit monitoring bureaus, TransUnion and Equifax, offer free credit-lock products. But locking down only two of your three main credit reports isn’t enough. You'll want to lock all three.

Not doing so is “like locking your front door but leaving your back door open,” Wu says.

Experian offers a subscription-based product called CreditLock through CreditWorks. It costs $5 for your first month of access and $25 per month thereafter.

Experian’s credit lock product also includes daily credit monitoring and alerts you if someone tries to apply for credit while the report is locked, as well as access to your FICO Score 8 and Experian credit report.

However, Consumers Union doesn’t recommend paying for credit monitoring. “What it does, consumers can usually do for free,” Tetreault says.

Another consideration: With a credit freeze, you won’t be targeted by ads.

“These lock services may allow the credit reporting agency to market to consumers more aggressively for products that they may not need and/or shouldn’t pay for,” Tetreault says.

Freeze Your Child’s Credit, Too

If you're considering freezing your own credit, remember that you can freeze your children’s credit, too. A child's Social Security number can be used by identity thieves to apply for government benefits, open bank and credit card accounts, apply for a loan or utility service, or rent a place to live.

But a lot of people don’t think about the vulnerability of their kids’ future credit, Rossman says. In a recent study, found that only half of U.S. adults had checked their own credit score or report in the 6 months after the Equifax breach came to light.

“If you’re not vigilant regarding your own credit, chances are, you’re not thinking of someone stealing your toddler’s identity and racking up fraudulent charges. This could potentially go undetected for many years until he/she grows up and starts applying for credit, only to find a big mess,” Rossman says.