GoogleForm で意図せず、同じフォーム入力の内容が送られてしまう問題とその対策

# 現象

GoogleForm において、ユーザがフォームを入力したあと、意図せず同じフォーム入力の内容が何度も送られてしまうという問題が発生しています。2020年の春ぐらいから現象が報告されているようです。

[Google Forms having duplication response entry within seconds](https://support.google.com/docs/thread/40862184)

[Duplicate responses to Google Form(Cheruwc)](https://support.google.com/docs/thread/40048414?hl=en&msgid=50440592)

[Duplicate responses to Google Form(Pavel Mamut)](https://support.google.com/docs/thread/40048414?hl=en&msgid=50538094)

(2021/6/15追記: まだ問題は続いているようです。)
[Duplicate Form Responses / Browser generating repeated submissions](https://support.google.com/docs/thread/104418993/duplicate-form-responses-browser-generating-repeated-submissions)

# 問題が発生する環境

iPhone 上の Safari(一部、Android でもというという報告もあり)

具体的には、Safari でユーザがフォームを入力し、入力完了画面をそのままにして、ホーム画面にもどる。しばらくしたあと、Safari を起動すると、ユーザが何をしなくとも入力した内容が改めてサーバに違うタイムスタンプと共に送られてしまうことがあります。

以下のサポートフォーラムでは、iPhone6S(iOS12) では「本当にこのフォームを再送信しますか？」というダイアログは出てくるが、iPhone6S(iOS 13.5) では出てこず、該当の問題が発生するとのこと：

https://support.google.com/docs/thread/40862184?msgid=59038117

> taypsl  7/15/20
>
> After experiencing this same issue of repeat entries showing up hours or days after, I  was able to determine that the form was resubmitting when a user returned to a tab with a previously submitted form on iPhone Safari. On an iPhone 6S running iOS 12, the user was prompted to submit the form again or cancel— hitting cancel did not result in a duplicate. On an iPhone 6S running iOS 13.5, however, there was no prompt, and the form automatically resubmitted when the tab containing a previously submitted form response was selected. Not sure if it’s an OS issue or a user phone settings issue... for now we’re adding instructions to close the tab when the form is completed to try to avoid duplicates in the future.

(2020/12/8 追記)
iOS や iPad の Safari 上のみで発生するようで、Chrome では発生しない模様です。 

https://support.google.com/docs/thread/40862184?msgid=86782538

> User 17380429347859411013
> 
> After a bit of testing I discovered that this only seems to happen when Safari is reopened after closing - whereupon it reloads the page, triggering the Form-Send.
I've also tested on my iPad -- and the problem occurs there too - again only when Safari App is rebooted thus restoring the page or when revisiting the page. 
NOTE - the issue does not seem to occur with Chrome browser on iPhone. Interesting that when you reopen the page, Chrome reloads a new blank form and does NOT capture the "success" page at all — a detail that should help developers pin down and fix the glitch. Also the response count when looking at the FORM  (design view) doesn't include the duplicates, these are only appearing in the response spreadsheet.

# 対処方法(WorkAround)

フォームを入力したら、ユーザにそのブラウザのタブを閉じてもらう。以下の操作になります。

https://dekiru.net/article/19314/

ユーザーがタブを残しておかなくても構わないのであれば、上記の記事で「見ていないタブを自動的に閉じる」の設定を「１日後」にしてもらうのがベストです。

https://support.google.com/docs/thread/40862184?msgid=73555813


> User 2701312192945702317 9/28/20
>
> I have diagnosed what the problem is.  When a form is Opened within a Safari TAB, that specific TAB is resubmitting the data ONLY when the user DOES NOT close that Form Input TAB.   If that submitted Form TAB is left OPEN then the NEXT TIME the user opens up Safari, Safari says oh RESUBMIT that OPEN TABS, Google Input Form data.
>
> Try this:  Open Safar, then Enter your Google Form and then CLOSE the Safari Application.   Then Open Safari and your still unclosed TAB which has your already submitted form in it, will resubmit the same data with a new timestamp.
>
> Now: Close all Safari Tabs or just the one with the Google Input Form.   Then start the process again by entering the Input Form and submitting in Safari, but after submitting CLOSE the INPUT FORM TAB.
Now close Safari.  Then OPEN up Safari and there will be NO DUPLICATE!
>
>To me this is a Apple/Safari Problem as this only started after their IOS update.  It would be nice if Apple and Google would work together to FIX THIS PROBLEM.
>
>It is ridiculous that I have to tell users to CLOSE an already submitted Input Form.
>
>Apple do something already.
>Mike

回答後のメッセージに、URL を記述し、必ずクリックするように注意書きしておくという手もあるそうです。入力完了のタブにおいて、ブラウザの戻るボタンを押してもらうのでもいいのではないかと思っています。

いずれにしても、根本的な解決にはなってはいませんが。


# Google の対応

https://issuetracker.google.com/issues/160714771