首先，also、as well、too 都有“也”的意思，大致有以下区别：
also 用在句中或句首，较常用于书面文本
Also 相较之下比较正式，常用于书面文本，一般放在句中或句首。放句中时常置于 be 动词及助动词后、一般动词前。例如：
The guidebook has been published and is also available for download online.（这本指南已经出版，也可以在网上下载。） also 出现在 be 动词后面
He is a famous pop singer who also writes poems and plays.（他是位知名流行歌手，也写诗和剧本。） also 出现在一般动词前
Frank Benjamin is the founder and also CEO of this company.（Frank Benjamin 是这间公司的创办人，也是总裁。）
此外，also 也可以放在句首用以加强语气。所以如果有句子是：
This documentary has gained wide attention and has also won several international awards.（这部纪录片不只备受关注，也赢得一些国际奖项。）
我们也可以将 also 移到句首来加强语气，写成：
= This documentary has gained wide attention. Also, it has won several international awards.（这部纪录片备受关注。此外，它也赢得一些国际奖项。）
as well 跟 too 通常用在句尾，而美式英文口语中更常用 too
As well 和 too 一般则用在句尾。在美式英文中，as well 又比 too 来得正式，一般口语中更习惯也更常用 too，但在英式英文中则没有这个差别。我们来实际看几个例子比较一下：
He’s a talented actor and also a popular columnist.（他是位才华洋溢的演员，也是位人气专栏作家。） also 放句中；较常用于书面
也可以用 too 和 as well 改写成：
= He’s a talented actor and a popular columnist too. too 放句尾；口语常用
= He’s a talented actor and a popular columnist as well. as well 放句尾；在美式英文中，as well 比 too 来得正式，口语上没有 too 来得常用；在英式英文中则都常用
He played the electric guitar and also drums.（他弹电吉他也打鼓。） also 放句中；较常用于书面
也可以用 too 和 as well 改写成：
= He played the electric guitar and drums too. too 放句尾；口语常用
= He played the electric guitar and drums as well. as well 放句尾；在美式英文中，as well 比 too 来得正式，口语上没有 too 来得常用；在英式英文中则都常用