Motivation to quit smoking hookah tobacco will be measured with a single valid item with a 7-point response ranging from 1 (not at all motivated) to 7 (very motivated) among those who are current hookah users. This item will be administered at all time points. A higher value on the response is considered a better outcome (i.e., more motivated to quit smoking hookah tobacco). Outcomes at the 6-month follow-up are reported.

Perceived addictiveness of hookah tobacco is measured using 2 valid self-report items (Mays, Tercyak, & Lipkus 2016). The items assess perceptions of how addictive hookah tobacco smoking is on a 5 point response (1= much less addictive than cigarettes, 5 = much more addictive than cigarettes) and how likely one is to become addicted to hookah tobacco on a 7 point response(1 = no chance, 7 = certain to happen). Greater perceived addictiveness and perceived likelihood of addictiveness (higher values) are considered better outcomes. The items are administered at 2-month, 4-month, and 6-month follow-up. Outcomes reported are for the 6 month follow up timepoint and represent the sum of responses to the two items. The sum ranges from 2 (min) to 12 (max) with higher values considered better outcomes.

Worry about the harms of hookah tobacco is measured using a single valid self-report questionnaire item (Mays, Tercyak, & Lipkus 2016). The item assesses how much participants worry about the risks of hookah tobacco (1 = Not at all, 7 = Very much). Greater worry about harm is considered a better outcome. The items are administered at 2-month, 4-month, and 6-month follow-up.

Worry about the addictiveness of hookah tobacco is measured using a single valid self-report questionnaire item (Mays, Tercyak, & Lipkus 2016). The item assesses how much participants worry about becoming addicted to hookah tobacco (1 = Not at all, 7 = very much). Higher values indicate greater worry about addictiveness and are considered a better outcome. The items are administered at 2-month, 4-month, and 6-month follow-up.

Total of all reporting groups

Participants in the hookah tobacco messaging group will receive hookah tobacco public education messages delivered online through 4 brief study communications. Messages will communicate about the risks of hookah tobacco use in the following theme areas: 1) Health Harms; 2) Addictiveness; 3) Social Use; 4) Flavorings. The order of message themes delivered in each study communication will be randomized.

Hookah tobacco messages: Messages communicating the risks of hookah tobacco use in 4 thematic areas: health harms, addictiveness, social use, flavorings.

Hookah tobacco use frequency will be measured in baseline current hookah users with a single valid question asking on how many days they smoked hookah tobacco in the past 30 days. Baseline current hookah users who reported they quit were coded as smoking 0 of the past 30 days. Less frequent hookah use is considered a better outcome.

Participants who were current hookah smokers at baseline and retained to the 6 month follow-up. Some participants retained did not answer all outcomes questions.

Hookah tobacco cessation is measured using a single valid question adapted from the national Population Assessment of Tobacco and Health (PATH) survey asking participants who report they have not smoked hookah tobacco if they have stopped smoking hookah tobacco completely. The item asks if participants have completely stopped smoking hookah tobacco based on a yes/no response. Quitting hookah tobacco use (i.e., a response of "yes") is considered a better outcome. The outcome measure data reports those who responded "Yes" and are considered to have stopped smoking hookah tobacco completely at the 6 month follow-up.

Participants who were current hookah tobacco smokers at baseline retained to the 6 month follow-up. Some participants retained did not answer all outcomes questions.

Curiosity to use hookah tobacco will be measured with a single valid item with a 7-point response ranging from 1 (not at all curious) to 7 (very curious) among those who are baseline susceptible non-users. This item will be administered at all time points. Outcomes from the 6-month follow-up are reported. A lower value on the response is considered a better outcome (i.e., less curious in using hookah tobacco).

Participants who were susceptible never hookah smokers at baseline retained to the 6 month follow-up. Some participants retained did not answer all outcomes questions.

Motivation to quit smoking hookah tobacco will be measured with a single valid item with a 7-point response ranging from 1 (not at all motivated) to 7 (very motivated) among those who are current hookah users. This item will be administered at all time points. A higher value on the response is considered a better outcome (i.e., more motivated to quit smoking hookah tobacco). Outcomes at the 6-month follow-up are reported.

Baseline current hookah smokers who were retained at 6 month follow-up and did not quit. Some participants retained did not answer all outcomes questions.

Perceived harm of hookah tobacco is measured using 4 self-report items. One item assesses perceptions of how harmful hookah tobacco use is (range 1 much less harmful than cigarettes to 5 much more harmful than cigarettes). Another item assesses how likely harms are to occur (range 1 no chance to 7 certain to happen). Another item assesses perceived harms of social hookah tobacco smoking in settings such as bars, cafes, and lounges (range 1 strongly disagree to 5 strongly agree). Another item assesses perceived harms of flavored hookah tobacco compared with unflavored hookah tobacco (range 1 strongly disagree to 5 strongly agree). For all 4 items, higher scores are considered better outcomes. The items are administered at 2-month, 4-month, and 6-month follow-up. Outcomes reported at 6-month follow-up reflect the sum of responses to the 4 items. The sum ranges from 4 (min) to 22 (max) with higher values considered better outcomes.

Participants at baseline who were retained to the 6 month follow up. Some participants retained did not answer all outcomes questions.

Perceived addictiveness of hookah tobacco is measured using 2 valid self-report items (Mays, Tercyak, & Lipkus 2016). The items assess perceptions of how addictive hookah tobacco smoking is on a 5 point response (1= much less addictive than cigarettes, 5 = much more addictive than cigarettes) and how likely one is to become addicted to hookah tobacco on a 7 point response(1 = no chance, 7 = certain to happen). Greater perceived addictiveness and perceived likelihood of addictiveness (higher values) are considered better outcomes. The items are administered at 2-month, 4-month, and 6-month follow-up. Outcomes reported are for the 6 month follow up timepoint and represent the sum of responses to the two items. The sum ranges from 2 (min) to 12 (max) with higher values considered better outcomes.

Participants at baseline who were retained to the 6 month follow-up. Some participants retained did not answer all outcomes questions.

Worry about the harms of hookah tobacco is measured using a single valid self-report questionnaire item (Mays, Tercyak, & Lipkus 2016). The item assesses how much participants worry about the risks of hookah tobacco (1 = Not at all, 7 = Very much). Greater worry about harm is considered a better outcome. The items are administered at 2-month, 4-month, and 6-month follow-up.

Participants at baseline who were retained to the 6 month follow up. Some participants retained did not answer all outcomes questions.

Worry about the addictiveness of hookah tobacco is measured using a single valid self-report questionnaire item (Mays, Tercyak, & Lipkus 2016). The item assesses how much participants worry about becoming addicted to hookah tobacco (1 = Not at all, 7 = very much). Higher values indicate greater worry about addictiveness and are considered a better outcome. The items are administered at 2-month, 4-month, and 6-month follow-up.

Participants at baseline who were retained to the 6 month follow-up. Some participants retained did not answer all outcomes questions.

Participants in the hookah tobacco messaging group will receive hookah tobacco public education messages delivered online through 4 brief study communications. Messages will communicate about the risks of hookah tobacco use in the following theme areas: 1) Health Harms; 2) Addictiveness; 3) Social Use; 4) Flavorings. The order of message themes delivered in each study communication will be randomized.

Hookah tobacco messages: Messages communicating the risks of hookah tobacco use in 4 thematic areas: health harms, addictiveness, social use, flavorings.