Ancestry's collection details crimes of men, women and children arrested and held at Swansea police station.
Convicts include Thomas Nash, the first murderer hanged privately at HM Prison Swansea, and William Boatwright, a 13-year-old egg thief.
Sentences ranged from corporal punishments to hard labour and fines.
The digital collection covers nearly 50 years of Welsh prison records and comes as part of a wider launch of more than six million records spanning 130 years, from original records held by West Glamorgan Archive Service.
The oldest felon to feature in the collection is Richard Evans, who was convicted for being drunk and disorderly and assaulting police aged 89.
Archibald Wilson Wall, 14, was convicted of stealing two tablets of jelly and two bottles of lime juice.
He was sentenced to one day in Cardiff Prison, and 12 strokes with the birch rod - but the friend he was arrested with, William George Parry, was sentenced to five years at a reformatory school.
Individuals would be held in county gaols and houses of correction until they were taken for trial in the Quarter Sessions, held four times a year, or Assizes, held bi-annually.
An archive of more than 120,000 historical records and images detailing south Wales' felons from up to 100 years ago has been launched.