Horse racing betting sites
A horse racing betting site is one of two very different things. Either it sends your bet into the track's own pool, or it keeps the bet itself and pays you an amount it decides. Work out which one you are looking at before anything else, because everything else follows from it.
How the pools, the takeout and the bets on a card work is on how to bet on horse racing.
Into the pool, or kept by the house
A licensed account-wagering service, where one is allowed, passes your bet into the track's pool. You get exactly what the tote pays, the same as at the window, and the track's takeout is the whole cost. Whether one can take bets from you depends on where you live, and racing has its own rules, separate from sports betting.
A racebook attached to a sportsbook, offshore especially, usually keeps the bet. It pays track odds up to a cap written in its house rules, and the cap is where the difference shows. Say the cap on a win bet is 20-1 and your horse wins at 40-1. At the track a $2 ticket returns $82. At the capped book it returns $42. The cap almost never matters on the favorite. It matters on exactly the tickets you will remember, the longshot and the big exotic, and I'd read it before the first deposit.
Rebates
Some pool-based services pay back a share of what you bet, called a rebate, and for anyone betting regularly it is the biggest difference between them.
Say you put $10,000 through the windows in a year, mostly in exotics, at a takeout of 20 percent. A bettor who does as well as the average ticket loses about the takeout, which is $2,000. A rebate of 3 percent of what you bet hands back $300, so your loss drops by 15 percent without picking a single extra winner. Rebate terms differ, some pay only on certain bets or certain tracks, and the best ones go to the biggest bettors. If I were betting seriously, it is the first thing I'd ask about.
The tracks and the data
A horse betting app is only as good as its card. I'd check which tracks it carries, at home and abroad, and whether it shows the race live and the replays afterwards. Past performances matter more than any feature on the screen: a site that gives you the full form for the races you bet saves you buying it elsewhere, and one that shows you only the odds is asking you to bet blind.
Watch how the app handles scratches and late changes. The odds you see when you bet are not the odds you get paid at, because the pool keeps taking money until the gate opens, and a lot of it comes in the last minutes. An app that refreshes slowly near post time shows you a price that is already gone.
Fixed odds
A few places offer fixed odds on races, where the price is locked when you bet, as a sportsbook does. That takes away the late drop, and it puts a bookmaker's margin in place of the takeout. Compare the two on the same horse before deciding which is cheaper; it is not always the one you'd expect.
For picking the horse, see horse racing betting strategies. For the money, set the day's budget before the first post, because an app puts the next race in your hand every few minutes, at every track it carries.
13 reviewed
Listed A to Z until our ratings are published.

BetanySports
Reduced-juice lines on the NFL, college football, NBA, WNBA, MLB and NHL, says the site. Crypto payouts in Bitcoin or Litecoin with no fee, up to $10,000 a request and $50,000 a week, as stated
25% sports free play up to $75Read the review
betDSI.com
Maximum bet up to $20,000 online or by phone, with higher limits on request, says the FAQ. Live betting across the major sports, a long props list and phone wagering
50% sports bonus up to $500Read the review
BetNow
Bet limits published by sport and day, up to $10,000 on an NFL side on game day, says the site. Deposits from $20, with no fee on crypto deposits
100% cash bonus up to $2,000Read the review
BetPhoenix
Toll-free lines in English, Vietnamese and Chinese, plus a wagering line, with online wagering 24/7, says the site. Live betting with games streamed on the site, as stated
175% free play up to $1,750Read the review
BetPOP
Crypto payouts from $50 to $10,000, twice a week, free, processed the same afternoon if requested before noon Eastern, says the cashier page. NFL sides up to $10,000 on same-day lines, with higher limits on request
50% free play up to $250Read the review
Bookie.ag
The bonus rules are written out, including what free play can and can't be used on. Support by live chat, phone and email in English and Spanish, around the clock, according to the site
100% free play up to $5,000, 18x rolloverRead the review
BookMaker Sportsbook
Crypto withdrawals from $50 up to $25,000 on weekdays, seven a week, with no BookMaker fee, according to its help centre. Live betting on all major North American sports, with props on NFL prime-time games, says the site
Bovada
Published withdrawal limits by method, up to $9,500 a Bitcoin request and $90,000 a week. No fee on crypto withdrawals, says the help center
50% sports welcome bonus up to $250Read the reviewBUSR
265+ thoroughbred and harness tracks with a daily horse rebate, says the site. Crypto deposits with no fees, and free Bitcoin payouts, as stated
100% Free Play match up to $1,000 on each of the first three depositsRead the review
JustBet
Maximum bet stated as $20,000 online and by phone, with higher limits on request. Crypto payouts with no fee from the book, according to its Bitcoin page

MyBookie
A 100% crypto first deposit bonus up to $1,000, with the rollover worked out on the bonus page. KYC-verified payouts processed within 48 hours, says the banking page
100% crypto first deposit bonus up to $1,000Read the review
WagerWeb
Bitcoin depositors can request payouts seven days a week, says the promotions page. Volume for rollover is the lower of risk and win, written out with examples
Progressive free play bonus, 10% rising to 50%, up to $500Read the reviewXbet
Bitcoin payouts typically sent within 12 to 24 hours, with a $25 minimum, says the help centre. Deposits by Visa, Mastercard, person-to-person and a dozen coins
100% crypto welcome bonus up to $200 in bonus betsRead the review