HTML5中的autocomplete屬性通過建議先前輸入的值幫助用戶更快填寫表單，從而提升用戶體驗(yàn)並減少錯(cuò)誤。它通過設(shè)置autocomplete="on"或autocomplete="off"控制瀏覽器是否自動(dòng)填充字段，且某些瀏覽器可能忽略敏感字段的“off”設(shè)置。要有效使用該屬性，應(yīng)結(jié)合合適的字段類型和有意義的名稱，並可採(cǎi)用具體令牌（如autocomplete="email"）以提高準(zhǔn)確性。常見用例包括登錄表單、結(jié)賬頁(yè)面和註冊(cè)表單；而應(yīng)在一次性敏感輸入、嚴(yán)格格式要求或非標(biāo)準(zhǔn)行為的字段中關(guān)閉autocomplete。合理使用autocomplete能提升可用性，而不應(yīng)盲目禁用。

The autocomplete attribute in HTML5 forms is a handy tool that helps users fill out form fields faster by suggesting previously entered values. When used correctly, it can improve user experience and reduce input errors.

What the autocomplete attribute does

The autocomplete attribute tells the browser whether it should automatically fill in a form field based on what the user has typed before. It works best when the browser has stored previous entries for that particular field or when the field matches known patterns like email, password, address, etc.

You can set it to either "on" or "off" :

• autocomplete="on" : lets the browser suggest values.
• autocomplete="off" : disables suggestions for that field.

Some browsers might ignore autocomplete="off" for certain fields (like username or password), especially if they have built-in password managers or autofill features.

How to use it effectively

To get the most out of the autocomplete attribute, pair it with appropriate field types and meaningful names or IDs. For example:

 <input type="email" name="email" autocomplete="on">

Also, for more control over what kind of data the browser suggests, you can use specific tokens instead of just "on" or "off" . These tokens describe the expected content of the field, such as:

• autocomplete="name"
• autocomplete="tel"
• autocomplete="address-line1"

Using these tokens makes autofill more accurate, especially on mobile devices where typing is slower.

Here are some tips:

• Use descriptive name and id attributes that match standard field labels.
• Don't force autocomplete="off" unless there's a real reason — like security concerns or custom input behavior.
• Test how your form behaves across different browsers and devices.

Common use cases and examples

There are many situations where enabling autocomplete improves usability. Here are a few common ones:

• Login forms : Email and password fields usually benefit from autocomplete being enabled, even if developers sometimes mistakenly disable it for perceived security reasons.

• Checkout pages : Fields like name, address, city, postal code, phone number — all work well with autocomplete tokens like "street-address" or "postal-code" .

• Registration forms : Fields asking for full name, date of birth, gender, etc., can be paired with tokens like "bday" or "sex" .

An example for an address form:

 <input type="text" name="fullname" autocomplete="name">
<input type="text" name="address1" autocomplete="street-address">
<input type="text" name="city" autocomplete="address-level2">
<input type="text" name="zip" autocomplete="postal-code">

These hints help browsers understand exactly what kind of data each field expects, so the right suggestions appear at the right time.

When to turn it off

There are a few valid scenarios where turning off autocomplete makes sense:

• Sensitive one-time inputs (like confirmation codes or CAPTCHA).
• Fields that require strict formatting not handled well by browser suggestions.
• Forms with dynamic or non-standard behavior, like masked inputs or auto-generated values.

If you're building a form where the user must manually enter a value every time — and any suggestion could cause confusion or error — then setting autocomplete="off" on those fields is appropriate.

But don't blindly disable it everywhere. Most users appreciate the convenience, and modern browsers are pretty good at handling sensitive data responsibly.

基本上就這些。

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