The effect of Sadako coming out of the well was accomplished with only one simple special effect. Rie Ino'o, who is a student of the Kabuki theatre, which uses exaggerated motion and jerking movements to emphasize emotion, was heavily involved in the development of the Sadako character. Ino'o was filmed walking backwards and the film was run in reverse - the end result is Sadako walking forwards with unnatural motions.

Shizuko Yamamura is based on a real person, Chizuko Mifune, who was born in 1886 in Kumamoto Prefecture and was rumored to have the gift of foresight. After a demonstration in 1910, she was proclaimed a charlatan and committed suicide a year later by ingesting poison.

The 2001 UK DVD release back cover carries a disclaimer, stating that the distributor accepts no responsibility for "for any injuries or fatalities that may occur during or after the viewing of this videocassette."

At the time of this film's release, it was the highest-grossing horror film in Japanese history.

The close-up of Sadako's eye near the end of the film was performed by a male crew member, Norihiko Miyazaki. Miyazakir had to chop off his eyelashes to make the shot more disturbing.

Kôji Suzuki got his inspiration for the Ringu novel from his favorite horror movie Poltergeist (1982).

The characters of Sadako and Shizuko are named after and loosely based on two real women. Both were taken under the wing of Professor Fukurai Tomokichi and, whilst not actually mother and daughter, Takahashi Sadako did work with the professor soon after Chizuko's suicide. Neither woman possessed the gift of nensha, but another student of the professor, Nagao Ikuko, was believed to have this power.

Sadako's psychic abilities are known as Nensha. It's a form of spirit photography that enables someone to burn images from their mind onto any solid surface just by thinking about them, which is why anybody close to her can suffer nightmares and bad visions. This is also how she burned her images onto the video tape.

Sadako is based on the legendary Japanese ghost of the Onryo. Usually female, it is a ghost that manifests after dying in the grip of a powerful rage and materializes as a very physical spirit to seek vengeance on the living. The Ju-On series was also inspired by the same legend.

The novel was originally science fiction based, while also blending in elements of supernatural horror as well. Hideo Nakata opted to remove the science fiction elements in favor of a more traditional ghost story. The sequel Rasen (1998) is more faithful to the source material, keeping the science fiction portions of the story.

The American trailer for Ringu pronounces the word as "ring-oo," but in fact, Japanese words must end either with a vowel or an -n. The "u" should be pronounced as a softly vocalized schwa; the word is taken from the Anglo-American verb, regarding the cyclical nature of Sadako's curse, and has nothing to do with the visual circular rings of the American remake.

Hideo Nakata would go on to direct The Ring Two (2005), a sequel to this film's American remake.

On its 1999 Hong Kong release, Ringu earned HK$31.2 million (US$4.03 million) during its two-month theatrical run making it Hong Kong's highest-grossing Japanese-language film. This record was later beaten by Stand by Me Doraemon (2014) in 2015.

In his film script, Hiroshi Takahashi changed the protagonist's gender (from male to female), name (from Kazuyuki Asakawa to Reiko Asakawa), marital status (from married to divorced) and child's gender and name (from daughter Yoko to son Yoichi).

Most of the film's shoestring budget (being $1.2 million) was provided by Hideo Nakata himself.

Hideo Nakata would go on to direct another film based on Koji Suzuki's literary works, that being Dark Water (2002).

According to director Hideo Nakata, the script and pre-production process took three or four months, shooting five weeks and post-production four months.

The entire film production only took nine months and one week to finish. According to director Nakata, the script and pre-production process took three or four months, shooting five weeks and post-production four months.

The special effects on the cursed videotape and some parts in the film were shot on a 35 mm film which was processed in a laboratory where a computer added a "grainy" effect.

Included among the "1001 Movies You Must See Before You Die", edited by Steven Schneider.

There was a limited theatrical release in Spain in 2016, only in Barcelona (Phenomena). The film was screened for 1 day with subtitles in 35 mm.

If looking closely at Sadako's hands, one can see that she lacks fingernails. This is a result of her trying to climb out of the well for seven days.

Sadako's face is never seen in the film. The closest we get to seeing anything resembling a face is the closeup of her eye.

Came 6th in the UK's "Greatest Scary Moments" for its shock ending.

In the novel, Sadako was actually an intersex woman with rudimentary male organs in her reproductive system. In the film, Sadako is quite clearly a female.