As a matter of fact, all your tweets will be stored on Twitter.com, but only those posted in about 10 days are available for search, and it is hard to track the old tweets, so that to back up your tweets will be useful, especially when you are going to review your old tweets.
To back up your tweets, you can check out below 10 websites, all of which will let you do that for free.
1. Google Reader
Just subscribe to your Twitter RSS Feed with your Google Reader, then you can back up your tweets automatically and you can also search them easily.
2. Twapper Keeper
On Twapper Keeper, you can back up any Twitter user’s public tweets just by entering its username, you can sort the results by date or the number of tweets, and you can also download the result tweets.
Besides your tweets, you can also back up the tweets with any hashtags or keywords.
Just enter any Twitter username, then you can review the tweets posted by the tweep and add them to calendar applications, such as Google Calendar. But some tweets may be missing sometimes.
Just log in with Twitter OAuth, then you can download your tweets as CSV files.
Besides your tweets, you can also back up your followers, friends, favorites, or direct messages, but you can only export the latest 1,000 tweets.
Go to Tweetake
Log in with Twitter OAuth, enter your email address, then your Tweets will be backed up automatically, and you can export them as CSV, XML, TXT or HTML files. But only a few tweets will be archived.
Log in with Twitter OAuth, then you can download your tweets when they are ready.
Besides your tweets, you can also choose to back up your @replies, friends, followers, direct messages or favorite tweets.
Go to Tweetscan
Sign in with Twitter OAuth, create an alert with any search term and the time you’d like to receive your Twilert, then remove the search term and enter your Twitter username in the From column.
Besides your tweets, you can also back up the tweets with any keywords, usernames or hashtags.
You can use Tweetbook.in to export your tweets as a PDF or XML file. Just log in with Twitter OAuth, then you can export your tweets with or without @replies, and you can also export your favorite tweets.
Go to Tweetbook.in
9. Google Buzz
You can sync your tweets to Google Buzz, then you can back up and review your tweets both on your Google Profile page or Gmail.
Go to Google Buzz
To archive some special tweets, you can favorite them on Twitter, or you can back up them with Evernote by adding “@myen” in the tweets or DM your tweets to @myen. To do this, you need to follow @myen, have an Evernote account and connect it with your Twitter account.
Among the above 10 websites, Google Reader is my favorite, since it is easy for you to search your tweets. How about you? Which one is your favorite? Or do you have any other websites to back up tweets? Share with us by adding a comment.