It is a cozy little hostel with a great location, right on the royal mile, the main street, and close to everything. Unfortunately, they only have 8 bed dorm rooms and breakfast is not included. They have free wiifii.

I stayed at the Royal Mile Hostel for two nights in mid March. The hostel is small and cosy and has a really laid-back and friendly atmosphere. The staff are young, easygoing and knowledgeable of places to see in Edinburgh. There's a fireplace in the reception area which was much appreciated, as the weather was chilly. Breakfast is available at an extra cost, but Wi-Fi is free (not very stable, though) and towels can be rented for only 20p. The location is perfect for exploring Edinburgh - it's only a 10 minute walk from the castle. I would definitely recommend this place to all backpackers travelling to Edinburgh.

The royal mile backpackers was my first hostel and I loved it.
The staff are very friendly and accommodating, making us feel more than welcome.
Now having stayed at at least 10 others I know it is definitely my favourite so far.
The only downfalls are the noise from the street n pub next door (nothing some earplugs can't fix) and only having 2 showers.
Would definitely recommend to a friend!

For reading the positive reviews this hostel has, I decided to book two nights at the royal mile backpackers, value for location, sleeping in a dorm seemed great, it is off the royal mile, just a couple minutes walk from the main attractions. Since I was already in Edinburgh i booked over the phone having to pay 1st night then to secure it. When I arrived there I wasn't able to see the room before I had payed my whole stay.
For my surprise the room was very dirty, cramped and looked like it hasn't been cleaned in ages, I had a small locker, but nowhere to put my backpack due to the amount of clothing and stuff placed everywhere, you need to add the body smell and hard beds to the sleeping experience. A friend was in another room and was exactly the same, but smell even worse (avoid staying at room 'starwars' if offered, it is unbearable).
It seems that some people stay here for long term periods and are not asked by staff to keep the rest of the other guests space free or keep tidy at all.
Bathrooms are ok, but only 2 and 2 showers, which means a sure queue in the mornings. And common space is reduced.
I did not see unfortunately the relaxed and cool vibe you get in other backpackers places. It was a big dissapointment.