MEXICO - The fate of tens of thousands of people seeking asylum at the United States' southern border will, from Friday, hinge on an app that has just 2.5 stars in the App Store.
For immigration managers, a sleek, computerised way to manage the wave of people expected to arrive when Covid-era rules lapse must have been tempting.
But for poor, exhausted people whose phones don't work, or who have no access to wifi or electricity, it's just another almost-impossible hurdle.
"It's amazing that an app practically decides our lives and our future," Jeremy de Pablos, a 21-year-old Venezuelan who has camped out in the Mexican city of Ciudad Juarez for weeks, told AFP.
De Pablos, who has dark skin, said the hardest part of using the CBP One app was the facial recognition -- an issue that many migrants with darker complexions have pointed to.
"It's like a game of chance. It recognizes who it wants to."
President Joe Biden's administration launched the Custom and Border Protection app in January, as it eyed a way to manage the expected chaos when Title 42 expires overnight Thursday into Friday.
The measure was imposed under Donald Trump, with a stated purpose of keeping those infected with Covid-19 out of the country, allowing border guards to refuse entry to anyone.
In practice it has been a quick and easy way to avoid accepting asylum claims.
But with the ending of the Covid emergency, Title 42 is finished, replaced instead with regular migration policies that the Biden administration says will offer pathways to legitimate asylum seekers, and harsh penalties to those who do not follow the rules.
- Old, outdated phones -
From Friday would-be migrants must register their name, date of birth, details of their travel documents, and upload a photograph on CBP One. The app can also log their location and their device details.
But old, outdated phones make the process hard.
It's harder still for those whose phones were broken or stolen on the long trek north.
Antonio Sanchez Ventura lives on the streets of Ciudad Juarez with nothing, eating only what he can scrounge.
His sole focus now is to raise the money to buy a phone and download the app.
"It is the dream of every human being to cross to the United States to help our relatives," he said.
- 'A nightmare' -
Ciudad Juarez is a tangle of tents and desperation, where people who have made impossible journeys scrape by on hope and charity.
Those who have phones search for exposed wires from street lights to charge them, and save every penny they have to buy credit to access the internet.
But the challenge does not end there.
"Look, it's stuck," said Ronald Huerta, a Venezuelan who on Wednesday couldn't get past the application's language settings.
A few meters away, Ana Paola, a 14-year-old Venezuelan, cried disconsolately because the application had been updated and all the information for her family had been deleted.
"I'm tired! I can't take it anymore!" the teenager shouted as she repeatedly clicked "Submit" to recreate the family's profiles -- receiving an "Error 500" message every time.
"It's been a nightmare, it's been a torment. This application has caused us emotional, psychological damage," said her father, Juan Pavon.
As Title 42 enters its final few hours, some migrants debate just sneaking across the border, hoping to avoid detection long enough to reach some kind of safety.
For some, the strategy works.
"I waited and waited and waited, but I got fed up, there was no way to get an appointment," said Luis Quintana, a Venezuelan who climbed through a hole in the wall at El Paso after three months on the streets of Ciudad Juarez.
For Raul Pinto, an attorney with the American Immigration Council, the app's many problems add another layer of unnecessary despair.
"It's frustrating that this important process is left at the mercy of technology that can often be glitchy and that is not going to be accessible by everyone," he told AFP.
The government said this week it would be rolling out updates to the app and increasing the number of appointments available in a bid to ease the logjam.
Pinto was hopeful that things would get better, but said there were many aspects of the process that were beyond fixing.
"We are very disappointed that there's not an alternative way for people to access this very important and potentially life saving process," he said.
By Paula Ramon