When is an auto-saving form appropriate?

Question

A trend Google has been pioneering in many Cloud applications is a sort of "autosave everywhere," especially noticable in Google documents's immediate save feature. I personally greatly prefer this functionality but it seems some situations clearly don't call for it; for example anything that might affect live data.

What affects whether a user should be in control of the save operation? So far I've considered:

Privacy/Security: Personal information like real names or information subject to attack like Credit Card numbers should only be submitted with her's explicit consent.

Ability to review: Gmail's draft feature is a good example of this; whatever you do is saved but nothing "real" happens until you hit the send button. I feel this could be applied to forms but the option seems a bit murkier there.

Discrete, reversible steps: If autosaved information may overwrite information it should be reversible. Google Docs addresses this by having a reversible "history" of edits, but makes the history fairly hard to use. Edits aren't grouped well so 10 minutes of editing might show up as 100 explicit steps to reverse. It's similar to Wikipedia's revision history feature, but that doesn't autosave.

Awareness: The most painfully annoying aspect I've encountered is when I don't know whether something has saved. Whether you want something to save and it doesn't or you don't expect something to save and it does, you're going to be mad.

What other considerations are there? What haven't I considered in the above list?

Answer 1

Here are considerations to add to your list:

HTTP requests

Depending on the profile and volume of your traffic, auto-saving forms can significantly add to your HTTP requests, thereby burdening your servers. If your volume is low or if server expansion is easy then go ahead, but be aware that there will be an effect.

New users

Some forms may not be saveable if a user is new and/or you don't have enough critical information to perform the save. For example, if a user is filling in a registration form, there wouldn't be much to save if all you know is salutation is Mr. and first name is 'Ben'.

Progressive Enhancement

It is important to make sure that as many users as possible can access your form successfully. While the numbers are decreasing and they may fall outside your target market, decide whether users not running javascript are important to you. If so, your auto-saving form should function perfectly well with a traditional save button that is, perhaps, hidden for those with javascript.