In terms of: costumes, dialouge, traditions and events.
Costumes: They were pretty good with costumes to an extent. They kept to the spirit but there were still some glaring inaccuracies. The one that stood out to me the most were the hairstyles and head jewelry of the women. Early 16th-century noblewomen would not have worn tiaras and the type of headpieces that showed in the series (i.e., https://www.google.com/search?q=the+tudors+tv+show&espv=2&biw=1436&bih=782&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjcx9K2os_NAhWHxYMKHRlEDzEQ_AUIBygC#tbm=isch&q=the+tudors+tv+show+headpieces&imgrc=J6DKtbYLbpQ0iM%3A or https://www.google.com/search?q=the+tudors+tv+show&espv=2&biw=1436&bih=782&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjcx9K2os_NAhWHxYMKHRlEDzEQ_AUIBygC#tbm=isch&q=the+tudors+tv+show+headpieces&imgrc=9TZsz8cPBqtZXM%3A). In the early part of the century (latish 1400s to around 1530s), which I guess if we are using the TV show chronology would be the very first episodes of the first season; English women would have worn what is called a gable hood. It was a pentagon shaped headdress with lappets in front that framed the face and covered the top part of the head and hairline. A veil would fall in back to cover the hair, which would be pinned perhaps in braids on the back of the head. Here's a good example: https://upload.wikimedia.org/wikipedia/commons/c/c0/Gablehood_front-back_c1535_detail.jpg Gable hoods were still popular up through the 1530s and then replaced with the French hood regarding fashion. The French hood was a round head piece that sat further back on the head so the front part of one's hair showed, however, the rest would be pinned back and hidden under a cascading veil. This type of headpiece was, funnily enough, popularized by Anne Boleyn who brought the style with her from France (she lived in France for a good part of her life since her father was the Ambassador to Paris). All this free flowing hair and long locks tumbling down the back in the show is completely inaccurate. In terms of the dresses, again, they kept to the spirit so they were recognizably of that century but not accurate. So popular fashion for gowns at the time would have been a separate bodice and skirt. The skirt would be coned shaped and had an open part in the front to display the forepart (which was richly decorated depending on your status) which was pinned to the petticoat. The bodice would have a square open, neckline, though sometimes women wore a partlet, which is an early equivalent to the ruff (which they were wearing in a few episodes which totally threw me) to cover up since the neckline was rather low. One thing that struck me about the shows costume was how tight the sleeves were on the gowns. The fashion at the time was to have trumpet sleeves, which were tight on the upper arm but flared on the lower. The jewelry wasn’t very accurate either. Chocker-like, layered necklaces were popular at the time and women would have worn a girdle type ornament dangling from their waste. Here’s perfect example of the fashion of the time https://upload.wikimedia.org/wikipedia/commons/5/53/Catherine_Parr.jpg I think the closest the show got to a completely accurate 16th century Tudor gown was Anne’s execution gown and Mary’s dark red and gold outfit from season 2. There also wasn’t so much cleavage; the corsets didn’t push up the breast so much as squish it. As for the men’s clothing, they forgot the codpieces (very important). There were also a few of Henry’s outfits where the skirt on the jerkin was much too long, they hit about lower-mid thigh which was popular with lower class men on the time but not a king. They also skipped around with the fullness of doublet and sleeves. By the 1540s full sleeves and doublets were in but Henry is consistently wearing fitted outfits. They also would have been wearing a lot of hats all the time.
Dialogue: The English court spoke French and have since the time of William I and would have spoken like Shakespeare were they talking in English. So, yeah dialogue is completely inaccurate.
Traditions: I don’t know what you mean by that but one thing the show did was leave characters alone in a room either by themselves or with one other person. I know they did that for drama reasons but it makes no sense historically. Like ordering maids or servants out of the room to talk in secret or have sex (I’ll get to that later) never would have happened. Never. Privacy meant only having a handful of people in a room so maybe you could pull someone to the side if you could but never alone. Everything was public, so elicit meet ups to go make out happening with nobody knowing, big fallacy. They also made women’s sexuality much more liberal in the show (to add the drama) than it ever would have been in real life. They also made the King out to have a lot more sexual power than he would have had.
Events: I only ever say the first two seasons and despite the not very clear passage of time, there’s a lot of historical inaccuracies here. Most of the big stuff did happen: the sweating sickness, Field of Cloth of Gold, birth of the bastard, Cardinal Wolsey, the divorce of course, etc. but so many things were just plain wrong that I can only list a few: • Henry had two sisters-Mary and Margaret- who were both smushed into one character. Mary married the King of France, the one before we see on the show, and Margaret married the King of Scotland which is why Queen Mary of Scotland had a claim to the English throne. Neither one was ever married to the King of Portugal nor was there ever any discussion of either one marrying the King. That whole storyline is completely fictitious. The character we see in the show is based on Mary, whose husband died early in their marriage and she did marry Charles Brandon. This all happened many years before the events of the first few episodes though. She dies in 1529 and the couple had four kids • Charles Brandon is a combination of two different historical figures. The real Charles Brandon was 7 years older than Henry and had had 2 wives before Mary • Anne Boleyn was not an attractive woman but she had beautiful dark, brown eyes. Guess the color of Natalie Dormer’s eyes? Henry was attracted to her wit and intelligence. He noticed her because she had already charmed the whole court. Yeah he wanted to have sex her but she wasn’t the sexual vixen she’s later portrayed as • Cardinal Wolsey did die from an illness, that wasn’t a cover up. The suicide was from a Shakespeare play. • Henry Fitzroy didn’t die as a child. He lived long enough to get married. • No one tried to assassinate Anne Boleyn • Jane Seymour was a lady in waiting to Catherine • Henry very reluctantly left Catherine, there wasn’t a conversation where he was like “I’m leaving you and we’re never having sex again and we’re getting a divorce” They were probably still trying for kids until everyone was 100% certain she was menopausal. Plus the show starts out around 1520ish and Henry wasn’t thinking about divorce until 1527. The shows moves fast • Catherine was also short and had blonde hair • Anne Boleyn probably wasn’t a reformer. We don’t actually know how she felt about Luther or Church reform but over the centuries she has been pinned as the reason for England leaving the Church There’s a lot more, but only some much I can write