The £750,000 acquisition will be funded from a £1.2mln direct subscription by the Downing Strategic Micro-Cap Investment Trust at 4.9p a share.
Tab Media operates a national website and 32 sub-sites individually focused on UK universities.
Revenues were around £1.2mln last year, giving a £400,000 loss before tax.
Digitalbox chief executive James Carter said: “The Tab provides a really exciting addition to our portfolio.
“As well as providing insights into youth and student culture, it is an important training ground for journalists.”
Digitalbox said its technology platform will be used to help drive traffic and advertising revenue to support the Tab site in much the same way as it has been deployed to support other titles.
“Since we acquired The Daily Mash in 2019, we have grown traffic and revenue whilst allowing the editorial team to get on with what they do best, and we aim to do the same with the Tab,” Carter added.