>>33523andMe and Ancestry.com DNA tests.
They say I'm mostly English by blood.
Minimum 65% but likely up to 85%, the rest would be Irish but I have no Irish surnames or communities in the most recent ~200-300 years of family history so the remainder is almost certainly English.
Got some northern French and maybe some Belgian as well. My surnames for the past several generations all also trace back to mostly southern/south-southeastern England and northern France.
Then I've got some Nordic/Finnish (5-10%) and speckles of Sardinian, Indian, West African, Native American, etc. Some of that could be genetic noise, or in the case of West African (Senegalese) blood, a slave could be in the bloodline somewhere.
There's a chance the French/Belgian in me could be German but it's unlikely given the surnames that turn up in the family history. Most can be traced back to English immigrant communities with a few notable French settlers. A few English and one French branch can be traced back to England and France. Notably Kent, England and Nord-Pas-de-Calais, France.
I'm also a registered Native American. 2 or 3 different tribes. Sub-1% contribution to my DNA though.
The tests don't work quite so well on women, but for men, they trace the Y chromosome back and find where your ancestors likely lived. For women they have to use X chromosome data and it provides only a general region in which they lived.
For example, my data narrowed me down to a concentrated area along the English Channel. My mother took the test and it only told her "Western Europe" and highlighted everything from north Spain up to Denmark and down to Switzerland with some of Norway/Sweden indicated as well.