Enter your birth details and this reads the parts of the chart a jyotishi looks at for marriage: the 7th house and its lord, Venus and Jupiter, the navamsa (D9), the darakaraka and upapada, manglik with every exception named, and the periods when the dasha and the transits of Jupiter and Saturn line up on your 7th house.
It shows the working, not a verdict. Nothing you type is stored.
A kundli shows periods the tradition associates with marriage: the dasha of the 7th lord, Venus and related grahas, especially when Jupiter and Saturn both fall on the 7th house. These are windows, not a date, and people decide the rest.
For the lagna, the houses and the navamsa, yes. Without it this uses your Moon sign as the first house, the traditional fallback, and says so.
In Jaimini astrology, the graha with the lowest degree within its sign among the seven. It is read as a significator of the spouse.
No. Many charts that count as manglik also meet one of the classical exceptions, which this tool names, and two manglik charts are traditionally treated as cancelling each other.
No. The chart is computed, returned and forgotten.
Learn the rules behind each part in the marriage astrology guides, or make your full janam kundli.