The cost of uncovering family histories online can be steep. What do you get in return?

Is digging up your ancestry online worth it?

NEW YORK — Genealogy is hot again.

Shows such as “Faces of America” on PBS and “Who Do You Think You Are?” on NBC are renewing the country’s fascination with family histories. And unlike when the TV series “Roots” aired in the 1970s, consumers now have numerous tools to dig up their ancestral pasts.

Websites that enable you to research your family tree or submit to DNA testing can be costly, however, and the results likely won’t be as dramatic as shown on TV.

It should also be noted that services can be limited depending on your family heritage.

Here’s a look at what three major sites offer.

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Ancestry.com

How It Works: A monthly subscription gives you access to 4 billion public records, including Census records from 1790 to 1930.

To help wade through the database, start by filling in a family tree with whatever information you have. If you punch in a grandparent’s name and approximate date of birth, for example, the site turns up public records that may be matches.

Users can make family trees public too, so those created by others will turn up in a search if you share a common relative.

When testing the site, a colleague with a common Irish last name quickly uncovered new information on her family. Within a few minutes, she found a photo of her grandmother that a relative had uploaded, as well as a Census record on her maternal grandfather.

How much your own search digs up will depend in part on how long your family has been in the country.

Records from outside the U.S. cost extra and largely come from the United Kingdom, Canada and Australia.

It should be noted that the site has considerable records for African Americans, including documents from the Freedman’s Bank and Freedmen’s Bureau, which were set up for freed slaves after the Emancipation Proclamation in 1863. Records from before then are much sparser, however.

Cost: $19.95 a month or $155 a year for U.S. records. If you also want access to records from outside the U.S., it’s $29.95 a month or $299 a year.

It’s free to set up a family tree and add your own photos and documents. If you cancel a paid subscription, access to the site’s documents is cut off, but you keep your family tree and any information uploaded.

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FamilyTreeDNA.com

How It Works: DNA samples are generally used to identify your deep maternal or paternal ancestry. The tests don’t provide a breakdown of your ethnic background. Instead, they trace single lines of DNA passed from generation to generation. So even if you know that your family is predominantly Irish, you might learn that the lineage on your father’s side traces back to Scandinavia.

Because only men carry a Y chromosome, women can’t get paternal lineages tested on their own. However, they can trace that side of their family by having a male relative tested.

The testing process is fairly simple. You get a collection kit to scrape the inside of your mouth with a cotton swab and mail the sample back. Results come back within several weeks.

At FamilyTreeDNA, samples are matched against a database of 190,000 men and 110,000 women.

For paternal lineage tests, you get a break down of individuals who matched your DNA by country. So you might find that the majority of your matches are of Italian descent.

The test for maternal lineage looks at what’s called your mitochondrial DNA.

A basic mitochondrial analysis only provides an idea of broader regional roots, although a fuller analysis can narrow results down to countries.

Anyone who buys a test gets an online account to access and interpret the results. You can also opt to make your name and e-mail available to those who match your DNA.

The number of matches you get will vary depending on your background. Those with English, Irish or Scottish ancestry might get several dozens of matches because those ancestries are well represented in the database.

The site has about 3,000 to 4,000 samples from Africa. Other groups, such as Asians, may turn up few or no matches.

The site guarantees your privacy, www.familytreedna.com/privacy-policy.aspx.

Cost: It’s $169 for the paternal lineage test. The basic maternal lineage test is $149, or $299 for a more detailed test. There’s a $4 postage fee.

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AfricanAncestry.com

How It Works: As the name implies, the site is tailored to African Americans. Its database includes 25,000 DNA samples from the African continent, with an emphasis on the Western and Central regions where the slave trades drew from.

Individuals can test their maternal or paternal DNA to see if either comes from African ancestry. If so, the test tells you the present day countries and ethnic groups that are a match. About 65 percent of those who get their paternal lineages tested find they are from African ancestry, while 92 percent of maternal lineages trace back to Africa.

Results include a printout of your DNA sequence, an African country reference guide and an online account so you can connect with other members.

The company guarantees your privacy; cheek swabs sent to labs contain no personal identification information.

Cost: $349 for either a maternal or paternal lineage test, or $300 each if you get both. The site runs specials throughout the year too.

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If you have a consumer question or comment, e-mail Candice Choi at cchoi(at)ap.org.