Welcome to the updated version of this post. The original, written 18 months ago, is now out of date because Twitter made a number of changes, first gradual and then more dramatic (before reversing them again) to what happened when person A blocks person B. If you want to read the original post it's available as a Word document (5 pages!).
If you want to see, in pictures, what someone you've blocked can see of your tweets have a look at "Blocking someone on Twitter - what can they see? (14 January 2014)"
Table of Contents
- The short version
- What happens if you block someone on Twitter?
- What happens if they block you?
- The longer version
- Historical problems with blocking
- How to stop someone from contacting you
- How to stop someone from reading your tweets
- How do you know if someone has blocked you?
- How to read the tweets of someone who's blocked you
- Private accounts - what to watch out for
- Further reading
1. The short version
- Blocking someone does not stop them from seeing your tweets. Period.
- Blocking someone does stop their tweets from appearing in your timeline / mentions (though you can still go looking for those tweets).
- If you want to make sure that someone cannot see your tweets then you need to make your account private, be cautious about who you allow to follow you (are you sure they've not just created another account to follow you with) and hope that their accounts aren't compromised by someone who'd cracked or phished their password.
1.1 What happens if you block someone on Twitter?
Not much. Their tweets won't arrive in your timeline or mentions tab - you won't hear from them. They can't follow you but they can visit your profile and search and still see everything you tweet though. If you are following a hashtag that they are tweeting on then their tweets will show up when you search for that hashtag (unless you search #hashtag -TheirTwitterName)
1.2 What happens if they block you?
Not much. Your tweets won't show up in their timeline or mentions, they won't hear from you. You can still see their profile but you can't follow them.
2. The longer version
Here's some nice music to listen to as you read on - I heard of it via Radiolab's Colors episode. This works on an iPhone and even plays in-page :)
The purpose of blocking, as Twitter sees it, is to prevent someone from contacting you via Twitter.
Any tweets that a blocked person sends to @YourTwitterName won't show up in your mentions or interactions. However if you search for all mentions sent to you (by literally typing @YourTwitterName into the search function) you can see any tweets they've sent you.
https://twitter.com/search?q=%40JoBrodie%20&src=typd&f=realtime = these are all public tweets sent to me (excluding those from private accounts, you won't be able to see those unless you're logged in as me). Replace the bit in bold with your user name to see tweets sent to you.
Anyone see your tweets, unless your account is locked and all your followers are trustworthy and haven't had their passwords pinched.
2.1 Historical problems with blocking
Twitter previously set things up with blocking so that if you tried to view the account of someone who'd blocked you you couldn't. Instead you'd be shown a page saying "this user hasn't tweeted yet" or similar.
This is no longer the case. Because people quickly worked out that all you had to do (then) was search for tweets from (or to) them or view their profile from a browser where they weren't logged in it was clear that blocking didn't mean very much.
Given the somewhat "fatal" flaw (that Twitter can't tell you're you if you're logged out) I think Twitter made the right decision to make it clear, as they've since done, that everyone can still see everyone else's account. I don't know when this happened but I noticed it in October 2012 when an alternative therapist blocked me (and provided a useful test-case for me finding out about blocks). Initially I couldn't see their tweets (without logging out), then suddenly I could.
Twitter has made it much less obvious if someone has blocked you (this is deliberate).
2.2 How to stop someone from contacting you
Block them. But note that it only stops that account from contacting you via Twitter, it doesn't stop that account (or a new one they've just created) from reading your tweets.
You can use the following links to restrict your mentions / interactions to only those who you're following.
• Mentions: https://twitter.com/mentions?filter=following
• Interactions: https://twitter.com/i/connect?filter=following (this one includes 'X favorited you tweet')
2.3 How to stop someone from reading your tweets
Lock your account. This will stop everyone from reading your tweets, unless they're already following you - many people don't want that. There is no way to stop only one or two people from reading your tweets. See (3) on Private accounts for more on the potential weaknesses of locked accounts.
2.4 How do you know if someone has blocked you? [Updated 15 January 2014]
It may depend on whether or not you'd previously followed them. I've tried this out myself with a test account and posted what I saw here (Blocking someone on Twitter - what can they see? (14 January 2014)) but it may not be the same for everyone.
If they've blocked you then you'll see a 'Follow' button on their profile. If you try and follow them a popup will appear telling you that you can't, because the person has requested that you can't. However if they haven't blocked you they will now get a notification that you're following them - so I don't know of any way to find out if they've blocked you that doesn't risk alerting them if they actually haven't!
Similarly if you try and favourite or RT one of their tweets you'll get a message saying your account can't do that (with favouriting you don't get a message as such, just that it's impossible to make the favourite 'stick'). They aren't notified of this if they have blocked you, but of course if they haven't and you've just faved or RTed their tweet, then they'll know.
2.5 How to read the tweets of someone who's blocked you
Just go to their profile - http://twitter.com/TheirTwitterName or log out.
3. Private accounts - what to watch out for
A locked account means that only people you've granted access to can follow you. New followers must request permission to follow which you can grant, or not. Since people don't have to use their real names to create an account you may not know if they're someone you want to let follow you or not.
For the slightly more worried...
If you know the email address of someone you may be able to find out what their Twitter name is - you can use the 'find friends' feature of Twitter in the settings to let Twitter access the email addresses in your contacts list.
You can also stop people from finding out, from your email address, what your Twitter name is by making sure that the " " option is unticked (I think unticked is the default setting) in the Security and Privacy section of your settings.
Remember that the security of a locked account is only as strong as the security of your followers - if one of them has their account compromised then anyone viewing their account can see your tweets.
Also, even people who are legitimately following you can still take a screenshot of your tweets and share that, or manually retweet your tweets by copying and pasting the text.
More about locked Twitter accounts:
- How to view private tweets - and what to be aware of to protect your account (7 December 2013) - as far as I know it is not possible to view the tweets of a private account but this shouldn't lull anyone into a false sense of security
- Don't assume that your private Twitter account is all that private (7 December 2012) - every tweet sent in reply to a private tweet can give some information about what was in the private tweet, a bit like hearing only one side of a phone conversation lets you guess what the other person said.
At the risk of lengthening this blog post to the point of ridiculousness I thought I'd try and answer directly some of the questions that people type into Google that bring them here. I've no idea who it is that's searching (I just get a list of search terms in Google Analytics) and I've turned the keywords into more readable questions.
If you block someone on twitter can they see your tweets?
Yes, they can do this by viewing your profile, searching for tweets sent to or from you, finding tweets in a hashtag stream or logging out.
If you block someone on twitter can they mention you in their tweets?
Yes, although it won't show up in your mentions / interactions tab - you'll have to search for your mentions (eg type @yourname into Twitter's search), search for their tweets, or visit their profile page. But they can still talk about you and converse with others mentioned in your tweets.
Can they retweet me if I've blocked them?
Yes, but only by copying and pasting the text and retweeting manually. You won't know that they've done this unless you look at their profile or search for their tweets.
How do you know if someone has blocked you on Twitter?
At time of writing (4 January 2014) I don't know of a foolproof way, without alerting them at least.
Probably you won't be able to use the Retweet button on their tweets, but if you try and retweet it (and can) they'll also get a notification that it's been retweeted. Similarly you won't be able to follow them (and Twitter might tell you that 'you have been blocked from following this account at the request of the user') however if they haven't blocked you, they get a notification that you've followed them.
Will someone know if you've blocked them on Twitter?
Possibly not. They certainly won't get a notification but they may be able to work it out from trying to interact with your tweets as above.
Can a blocked twitter user still see your direct messages?
I don't know for certain (not having been in that situation). I suspect that because blocking them effectively stops them from following you then they will certainly be unable to send any new DMs but I don't know if any previously sent DMs will simply disappear. If you have sent them any DMs the safest option is to delete them - this will also delete them from their inbox (as only one copy is available).
Can people tell you've been looking for them or their tweets on Twitter?
Not as far as I'm aware. To the best of my knowledge Twitter does not make information available to users about what people have been searching for (and remember you can also search Twitter from outside of Twitter itself using Google, by searching for site:twitter.com keyword, and Topsy.com among other tools). So in that sense probably not.
But if you come across a tweet and respond to it then you've kind of given yourself away there ;)
Can you still view tweets when not logged in?
Yes, as long as those tweets don't belong to protected accounts, you can still see everything you just can't interact with them. Twitter's homepage (http://twitter.com) is a bit unwelcoming if you're not logged in so it helps to know the address of the profile you want to look at (eg http://twitter.com/ScreenName) and the basic search address which is http://search.twitter.com
Other than going private, is there a way to stop someone from seeing your tweets?
No. Blocking doesn't even do this (if they log out they can certainly see your tweets and even if logged in they can search for them and they'll probably show up in the results too). Protecting your account is the only way to stop someone seeing them - but you have to trust that everyone whom you've allowed to follow you isn't going to retweet your tweets without permission and give the game away.
On Twitter what does 'we block eggs' mean?
When someone is new to Twitter they have the symbol of an egg as their picture (avatar) which they can then change to something else. Spam accounts are often created just to send the same link to a lot of people, they don't bother to change the picture so people associate these eggs with spammers and are wary. Not all spammers have the egg picture and not all people with egg avatars are spammers, but it is a 'risk factor' for an account to be treated more cautiously.
I'd never heard the phrase used before (people usually say "I block..." and they usually talk about blocking spam accounts, to me 'we' is an unusual word to write on a Twitter account unless it's an organisational one) but it seems that this is a phrase that has been used on a few accounts shared by married couples looking for *ahem* other people for fun and games. Well that was a bit of an eye-opener ;) This will take you to the search page for that phrase, there's nothing particularly saucy there, just info about accounts who use that phrase in their Twitter bio https://www.google.co.uk/search?q=%22we+block+eggs%22
Presumably people who are using Twitter to talk about these interests are more likely to be targeted for spam and so have a lower tolerance for such accounts. You learn something new every day...
5. Further reading
It appears that Twitter's reversed some / most / all of the changes in response to the complaints.