When it comes to streaming services, the first names that come to mind probably include Amazon Prime, HBO Now, Hulu, and Netflix, which offer hundreds of titles, including recent releases and original TV series.

One thing these services have in common is that you have to pay.

But consumers can also stream movies free, from services that are—in most cases—supported by ads. The best bets among these services include Crackle, Kanopy, Pluto TV, and Vudu.

Like Netflix or Hulu, these free services are available on most streaming devices, making it easy to watch on your TV, laptop, or tablet.

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In addition to making you sit through ads, such services bring some other trade-offs. You’re out of luck if you want Ultra High Definition, or 4K, shows. Instead, these services provide regular HD video, as do cable-TV companies. You’re not likely to find very recently released movies. And, of course, you won’t be able to watch original shows such as HBO’s “Game of Thrones,” Hulu’s “Runaways,” or Netflix’s “Stranger Things.”  

But in a world of $1,000 smartphones and $5 salted caramel mochas, it’s nice to know you can still see “Fiddler on the Roof” or “Lethal Weapon” free of charge. (Another path to free content is to get a TV antenna.)

Here’s what you need to know to stream movies free from the services mentioned above. They appear here in alphabetical order.

Crackle

Crackle, Sony’s ad-supported streaming service, hosts a library of mainstream titles, including older TV shows (“Seinfeld,” “Walker, Texas Ranger,” and “Who’s The Boss”) and popular older movies (“Lethal Weapon,” “Terminator 2: Judgment Day,” and “Total Recall”).

And the service has a smaller collection of more recent movies, including “300” and “Sherlock Holmes: A Game of Shadows.”

Like Amazon, Hulu, and Netflix, Crackle has been developing some of its own content. These series include “Snatch,” a drama based on the movie of the same name, and “StartUp,” which is essentially a darker version of HBO’s “Silicon Valley.”

Kanopy

Unlike the other streaming services on this list, Kanopy doesn’t show ads. But to use the service you’ll need a membership at a participating library, university, or other learning institution. 

Kanopy says it has a catalog of 26,000 films, from sources including the Criterion Collection, the Great Courses, New Day Films, and PBS. If that sounds like a cerebral list, it is—Kanopy’s selection leans away from Michael Bay blockbusters and toward art-house files. Indie flicks include “Dave Made a Maze” and “Hunt for the Wilderpeople”; available documentary titles include “America Divided” and “I Am Not Your Negro.” 

If you access Kanopy through a library membership, you may be able to watch a limited number of titles per month; members of educational institutions get unlimited access. 

Kanopy maintains a list of participating institutions. The same page lets you request access for your library if it doesn’t participate. 

Pluto TV

At first glance, Pluto TV looks a lot like the navigation menu from a cable box, with scores of channels.

These aren’t familiar broadcast channels, however.

Most of the channels feature video content curated from around the web, including online newscasts from CBSN, Cheddar, and NBC News, as well as comedy content from Mystery Science Theatre 3000 and The Onion.

But Pluto also offers more conventional streaming-service content, including both modern movies (“Crash” and “The Hurt Locker”) and classics from earlier eras (“Fiddler on the Roof,” “The Great Train Robbery,” and “Some Like It Hot”).

Compared with its competitors, Pluto TV seems somewhat hit-or-miss in terms of selection. The TV show selection is particularly sparse, though it will satisfy fans of  “Fear Factor USA” and the British comedy “The Inbetweeners.”

Vudu

Vudu is best-known as a paid site, where you can buy or rent a wide range of movies and TV shows. But site also has free content, which you can find under a Movies On Us tab at the top of the home page. 

The offerings aren’t nearly as robust as the rest of the Vudu catalog. But the rotating collection of free stuff includes some very popular older titles such as, recently, “Interstellar,” “Titanic,” and “True Grit.”

To use Movies On Us, you’ll need a Vudu account, but you don’t have to provide payment information.