There are a total of 60 teams in this round, 52 of which are in the main path. Eight teams who lost in the Champions League first qualifying round are involved in a dedicated champions path.
Turkish club Istanbul Basaksehir were made to sweat in their match, as they fell behind less than two minutes in away to Viking. Sander Svendsen put his team in front as a potential upset looked to be on the cards.
The hosts continued to create chances in the opening half as Joel Bell had a glorious opportunity half an hour in. Unfortunately for him, Basaksehir had enough players back to get a piece of the shot.
Failing to make the most of their chances, Viking were ultimately punished in the second 45. Deniz Turuc tied things up at the hour mark, before Christopher Operi netted what proved to be the winner 11 minutes from time. Davie Selke added a third in the final moments to give Basaksehir a 3-1 win heading into Tuesday's decider.
Elsewhere, Slovenian side Celje, who reached Conference League's quarter-finals last term, ran rampant in a 5-0 defeat of Lugano. Franko Kovacevic scored two penalties - one in each half - as the visitors converted their chances in a resounding victory over the club they knocked out of the competition at the round of 16 last March.
CS Universitatea Craiova found three goals in the second half in their 3-0 success over Spartak Trnava. The Romanians, who reached the semi-finals of the 1982/83 UEFA Cup, scored twice in the space of three minutes shortly after the restart as they take a commanding lead with them to next Thursday's decider.
Banik Ostrava and Austria Wien were involved in an entertaining clash in Czechia, as the hosts found themselves behind just four minutes in. However, they ended taking a 2-1 lead with them into half time, before adding a third minutes after the restart.
The Austrians ended up drawing level in the 79th minute, and just when they thought they would claim a draw, Erik Prekop scored the winner to give Banik a 4-3 win and a narrow advantage.
It was a successful day for losing teams from the Europa League second qualifying round. Anderlecht enjoyed a 3-0 home success over Sheriff Tiraspol, while Besiktas got past St. Patrick's Athletic 4-1. Hibernian recovered from their heartbreak of last week Thursday with a 2-0 win over 10-man Partizan Belgrade. As for Levski Sofia, they edged Sabah Baku 1-0 thanks to 98th minute winner through Branislav Rupanov.
In the champions path, FCI Levadia Tallinn came out on top 3-2 versus Differdange 03 as the Estonians did their damage before the hour mark. That was also the score in Moldova, as Milsami Orhei managed to beat Virtus despite going down to nine men with seven minutes left. Still, Ime Ndon found a winner for his team just before the end of the 90 minutes to give them the upper hand in next week's second leg in San Marino.
The return legs are next week Thursday, save for Basaksehir's game against Viking.
Follow the UEFA Conference League qualifying round action on Flashscore.