His searches included phrases like "son kills mother for miscegenation", a word meaning the mixing of different racial groups through marriage, cohabiting, sexual relations and procreation.
Speaking after Mair's whole life sentence was handed down, Mr Cox said: "To the world, Jo was a member of Parliament, a campaigner, an activist and many other things.
"But first and foremost she was a sister, a daughter, an auntie, a wife, and above all a mum to two young children who love her with all their being.
"We try now not to focus on how unlucky we were to have her taken from us, but how lucky we were to have her in our lives for so long.
"To the person who did this we have nothing but pity - that his life was so devoid of love and consumed with hatred that this became his desperate and cowardly attempt to find meaning," he added.
"The killing of Jo was a political act, an act of terrorism, but in the history of such acts, it was perhaps the most incompetent and self-defeating.
"An act driven by hatred which instead has created an outpouring of love. An act designed to drive communities apart which has instead pulled them together. An act designed to silence a voice which instead has allowed millions of others to hear it.
"As a family, we will not respond to hatred with hatred. We will love like Jo did and know that, although she is dead, the ideas and values that she held so dear will live on.
"We hope the country will also take something from this - that Jo's death will have meaning.
"That those in politics, the media and our own communities who seek to divide us will face an unassailable wall of British tolerance and the articulation of Jo's belief that we hold more in common than that which divides us."
A white supremacist has been told he will serve the whole of his life in jail for murdering MP Jo Cox.
Thomas Mair attacked the 41-year-old mother-of-two as she arrived for her weekly surgery at Birstall Library, shooting and stabbing her after shouting "Britain first".
Mair, who had a stash of neo-Nazi material at his home in the West Yorkshire town, had pleaded his innocence but failed to offer any evidence in his defence.
The jury at the Old Bailey took just 90 minutes to find Mair guilty after a prosecutor described how, having failed in a first attempt to kill her, he came back to shoot and stab the Labour MP for Batley and Spen in front of her shocked constituents.
She was shot at three times and stabbed a total of 15 times a week before the EU referendum, in which she had been campaigning for the UK to remain.
Her constituency caseworker Sandra Major told jurors during the trial: "He was making motions towards us with the knife and Jo was lying in the road and she shouted out 'get away, get away you two. Let him hurt me. Don't let him hurt you'."
Passer-by Mr Carter-Kenny, 78, was stabbed as he tried to stop Mair by jumping on him from behind.
When he was swiftly tracked down by police a mile away, Mair's holdall contained the blood-splattered murder weapons including a reproduction Fairbairn-Sykes "fighting dagger", designed during World War Two for British special forces.
After his arrest, police uncovered a hoard of neo-Nazi literature at his council house and a golden Third Reich eagle ornament with a swastika emblazoned on the front.
Detectives investigating his use of library computers also exposed Mair's interest in far-right, anti-Semitic and neo-Nazi politics in Britain and abroad.
Sue Hemming, head of special crime and counter-terrorism at the Crown Prosecution Service, said: "Mair has offered no explanation for his actions but the prosecution was able to demonstrate that, motivated by hate, his pre-meditated crimes were nothing less than acts of terrorism designed to advance his twisted ideology."
Jo Cox was the first British female MP ever to be murdered and the first MP to be killed in office since 1990.
She was barely a year into her dream job when she died, yet had marked herself out as an MP with one of the brightest futures among the 2015 House of Commons intake.
Labour leader Jeremy Corbyn described the murder as "an attack on democracy" which "has robbed the world of an ambassador of kindness and compassion".
Home Secretary Amber Rudd said: "The shocking and senseless murder of Jo was an attack on all of us and the values we share of democracy and tolerance.
"As Home Secretary I am determined that we challenge extremism in all its forms including the evil of far-right extremism and the terrible damage it can cause to individuals, families and communities."