A glitch is a code or user error that causes a problem that can disrupt gameplay or site navigation.
Glitches vs. Exploits
Some people use these terms interchangeable. A glitch is generally accidental, and not abusable to further anything. An exploit is generally done on purpose, and it is used to further something, or to show off that you can "hack". Abuse of an exploit can be a bannable offense, if it is truly an exploit, and not a glitch. Abuse of glitches generally not so.
Wear robloxian 3.0 man head and square torso. Make sure all your body colors are the same and you have no clothing templates on. Some combos make your head not be there in game either.
Putting a wielded/any attaching surface brick on the back or front of your leg can cause you to 'fly' when you walk forward. You move up while going forward. Gravity is unaffected, so you drop when you are not walking. This is only seen in building places, because you generally cannot put a brick on yourself in any other game.
Freeze Ray Holding
When this glitch occurs, a player does not hold a freeze properly. It can occur in-game, or in a player's avatar.
If a user stands near an edge and then jumps, the player will go flying away from the edge and possibly result in a death. This is due to the in-game physics. It also occurs when you walk into a corner at the right angle. (As far as I know, this has been fixed.)
A player wearing an egg hat they can press '=' on the keyboard to remove the hat. Once the egg lands the user is able to jump on the egg and 'super jump'.
Endless Install Loop
This bug forces you to reinstall ROBLOX every time you click play on a place. To remove it, you must uninstall ROBLOX completely and then reinstall.
When certain items are equipped, most notably the ROBLOX Visor in 2007 or the Vampire Collar, the player's avatar is zoomed in upon the face. This does not affect your character in-game.
When certain items are equipped, such as the Dusek Car, 2013 Sparkler or the Sonic Boom Tuba, the player's avatar appears small. This does not affect your character in-game.
This is the most common glitch that appeared in 2011-2012. In 2011, if you press too many tabs and put something at the end it results as number appearing in your's and other players that has 13+ chat. The number are usually packed in boxes, but they blink and is stationary at one place. An example is "Hello (tabs) Telamon: Hi people!"
Sometimes, when the part the user's camera was focused on moved too fast, the camera would go white, and would not fix itself upon resetting. The only true way to fix this was to remove that player's local camera. The users's camera is now automatically removed when the user resets, so the user can reset and no longer have to worry about this.
Expanding on Expanded
(Baseplate is not the cause.) When you put a brick on wide/lengthy brick it will move for an unkown cause. Possible theories are border bricks on top and different formfactors. You can see the brick move pixel (not stud) by pixel if you use the expansion tool and force it to move where it is already blocked by another brick. The worst thing is when you move or delete a long brick that touches a piece the touches the long brick, the whole bricks touching the long brick moves.
This glitch causes your avatar to lose all clothing items besides hats, and have them replaced with toolbars, chats, terrain, and the cursor. It is most common on Macs, and does not go away. It does not affect the head, only the legs, torso, and arms.
In the chat, typing something, pressing Shift+Enter, and type another thing. Then pressing enter splits your chat box and bubble into two lines. This is similar to the tab glitch.
No Delete Button
In June 2010, the delete button was removed. If anyone took something from an item, the player could not delete it. He/she could get as many items you can if you wanted to but it still won't show up the button to delete it. Players who have an item before this will show up the delete button. This has been fixed now and players who bought a hat during this issue will now show its delete button.
A user named Nikayah created an exploit in which one of the hats, such as the Riddling Skull, was given out to over 1,000 users. ROBLOX has banned him and was unbanned with another exploit in early 2009. xSCENEx has also done this by giving the Teapot Turret to himself.
No Torso Glitch
This happened on December 15, 2010. This glitch allowed the player's avatar to have no torso. It didn't cause any problems with ROBLOX. His/her torso would be there if he/she joined a game. This was fixed and all players were updated back to normal on the 16th.
Gear Down GlitchThis glitch was only up for a few hours before it got patched. This glitch prevented the player's avatar to move its arm in the proper location while holding a gear.
The double gear glitch allowed users to drop one gear, and select another gear while walking over the dropped gear, which would let them hold two gears at once.