Halachic Perspectives on Wearing a Fitbit on Shabbat

Dear Rabbi, I have this problem and truly hope you can help me. I've been wearing a fitbit watch during the week, to record my steps and my overall health, as I am trying to lose weight. However, as I'm observant, my biggest fear is remembering to take it off before Shabbat. I literally break out in cold sweat at the thought, and jump up in shock frequently, to check if the watch is still on my wrist during shabbat. Please tell me what I should do, if I accidentally end up forgetting to take it off? Is there a way out? TYSM, D.

Thank you for your question.

First, let me reassure you—you don’t need to worry or panic. When it comes to the world of halacha, there is always clear and direct guidance on what the right thing to do is in every situation. It’s good that you are asking and verifying the halacha; it's important to be knowledgeable and know what to do in every situation.

The Fitbit is a very sophisticated watch. It has sensors that are activated by the touch of one’s skin, and when one puts it on one's wrist, it immediately starts to record steps, heart rate, etc., tracking one's activities. Later, at the end of the day or even week, one will then connect the watch to a computer and the Fitbit app, and can then see a full record of one's activity—for example, if you were walking enough or exercising enough. One can analyze and compare his lifestyle, and it ultimately motivates one to improve and adopt a more healthy way of life.

This introduction will help us analyze the halachic aspect of owning such a watch with regard to Shabbat.

We know that on Shabbat, there are 39 melachot—forbidden activities—that one may not perform. These activities are based on the 39 melachot that were used to construct the Mishkan. So one could ask, but they weren’t wearing a Fitbit during the construction of the Mishkan. Here is the thing: the Talmud in Tractate Shabbat says that these 39 melachot are called the avot melachot, meaning they are the primary categories of work, and then throughout the generations, with the advancement of technology and innovation, the rabbis are able to compare each of these new discoveries and assess whether by using it, there is one of the 39 melachot at work.

For example, when it comes to using electrical devices on Shabbat, according to the Chazon Ish (Orach Chaim, Siman 50, Se'if 9), it may even be considered a melacha of boneh—constructing—since by turning on an electric device, one is completing an electric circuit, and this may well be an issur de'oraita. That is one of the reasons why one may not activate an electric device on Shabbat.

Wearing a smartwatch when it is on: When wearing a smartwatch, whenever one makes the smallest movement, it turns on the screen, and each step one takes gets recorded on the watch. Therefore, keeping it on one's wrist during Shabbat actively uses an electric device, which is forbidden.

Wearing a smartwatch when it is off: In a case where one switches off the watch but keeps it on the wrist on Shabbat, one might argue that now that the watch won't get turned on by movements, it is permissible to wear it. However, that is not the case since the sensors are still working and recording all your movements, and after Shabbat when you connect it to the computer, it will report all the details of your activity throughout the day.

This cannot be compared to say that it is melacha she'eno mitkaven (unintentional labor), which generally is permitted on Shabbat. Since when the watch is off, one has no interest in the labor taking place. For example, walking past a CCTV camera that is actively recording your movement is permitted because one has no interest in its recording. However, in our case, the watch is recording through its sensors for your records, so it is forbidden since you have an interest in it recording.

By mistake, one realizes on Shabbat that he is wearing a Fitbit that is on:

This is a problem since by taking it off one will actively affect the sensors and recording. However, keeping it on is also forbidden, so what do we do?

There are two options, the first better than the second. The first option is, if there is a non-Jew in the area, to ask him (try b'remiza, by hinting not direct command) to remove the watch; this way, it won’t be considered as you having done any forbidden activity. If that is not possible, then one should remove the watch with a shinui, like by one's teeth or little finger. This way, when a melacha is done with a shinui, since it is not the normal way of doing the melacha, b'dieved it won't be considered as having transgressed the forbidden activity on Shabbat.

So, we have discussed and explained that one may not wear a smartwatch on Shabbat, and it doesn’t make a difference whether it is on or off.

1. Tractate Shabbat, Talmud Bavli.
2. Chazon Ish, Orach Chaim, Siman 50, Se'if 9.