Marriage is read from the 7th house and its lord, and from Venus as Kalatra karaka. Strain is judged from the 6th (disputes), 8th (upheaval) and 12th (distance), and from malefics (Saturn, Mars, Rahu, Ketu, Sun) on those points. Benefics, especially Jupiter on the 7th or Venus, steady the meter.
The tool shows a 0-100 separation-possibility meter, contributing strain and support factors, and the heart of it: Vimshottari Mahadasha-Antardasha windows of the 7th and 6th lords, Venus and the malefics touching them. Extra patience in those windows is the classical advice. Love and effort still grow a marriage. This is not a prediction that a divorce will happen.
This page is dasha timing of marital strain, not a yoga checklist and not legal advice about separation, maintenance or custody. Those decisions belong to the people involved, a counsellor and, if needed, a lawyer. Discord yogas themselves are Divorce Yoga. Two-chart matching is Kundli Milan. When a first union is supported is Marriage Timing Possibility - Vivah Yoga. The natal chart is Kundli Maker.