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This article is about bugs in Scratch itself. For bugs in computer software, see Bug.

There are many notable bugs in Scratch. Some may just be graphical, some might impact coding, some might make text missing and some might show extra things. There are many minor bugs, but they are often fixed. However, some of them may impact the Scratch editor or website significantly.

Current Bugs

Mailbox Bug

In the Scratch website, the mailbox may show "0 Messages" rather than no number.[citation needed] A possible reason for this was that the mailbox did have messages but just showed the number '0'.[citation needed]


Wrong Font Bug

In the Paint Editor after the release of Scratch 3.0, sometimes the Sans Serif font displays as a larger Serif font.[citation needed] There is no known cause and solution for this bug, but the workaround is to use the Chinese, Japanese, or Korean fonts instead, as they all look very similar to the Sans Serif font. This is very similar to the Sans Serif bug (backdrop selector).

No Last Post Bug

Main article: No Last Post

In May 2017, when spammers were active, on some occasions the "last post" field next to a subforum description would be missing.[1] Though it died down after a while, later posts in the affected forums seemed to bring it back. A possible reason is that the last post was deleted.[2]

Disappearing Comment Bug

Main article: Disappearing Comment Bug

Mainly found in Scratch 3.0, this bug causes profile, project, or studio comments to not show when attempting to view it. Sometimes, when the message for the comment is clicked, the comment section will not load. Then, if a user tries to view the page where the comment is without the direct comment link, the comment will not be shown. This can cause the inability to view, reply, delete, or report the comment. To fix this, do a hard refresh.[citation needed]

Trending Glitch

Main article: Trending Glitch

In Scratch 3.0, the trending glitch is a way of getting one's project shown in the trending category of Explore without the project actually qualifying for "trending" status. Unsharing and then resharing projects utilizes the glitch by making the Scratch website believe that the reshared project received however many loves and favorites the project in question had before the reshare immediately as it was reshared when in fact the project had already received those loves and favorites before it was even shared. As a result, the project is mistakenly shown as "trending."

Percent Custom Block

The blocks bunched up after naming a custom block "%"

In the Scratch 3.0 project editor, naming a custom block "%" will result in Scratch not letting one press "OK." If one presses "cancel" after that, all the blocks in the Block Palette will be bunched up and display in the same location.[3] This bug can be fixed by going to a different sprite or leaving the "Code" tab.

Double Comments

As of March 2021, in Scratch 3.0, comments are sometimes duplicated.[citation needed] Sometimes, Scratchers will send 1 comment, and after posting the comment, see that they sent 1 comment, and leave the page.[clarify] Other Scratchers see it as 2 entirely same comments, which might be considered spam.

Automatic Logout Bug

The cookies sent by scratch:abouta
Note Warning: Visiting pages such as https://scratch.mit.edu/abouta causes one's account to be logged out, which may lead to one's recent changes to their projects being lost.

This is most commonly experienced when visiting a page such as scratch.mit.edu/abouta (notice the a, any string of text after 'about' can work). It is due to the website sending a malformed cookie.[4]

Thumbnail bug

Many Scratchers found out their projects' thumbnails reverted back to the default Scratch cat with a white background. This is seen in many projects and it is one of the most common bugs. This bug was reported on many topics and posts. It spread rapidly, and as of June 2021, it is still not fixed. It was first seen in May 2021. A simulation of this bug may be made within the animated project thumbnail set.[5][6] The exact cause is unknown but it could be because Scratch is unable to load the image.

Invalid Characters Bug

Main article: Undefined Hat Block
The empty Hat block.

Putting a control character (such the "NAK" character, and other characters) into the text box of a custom block results in an empty undefined Hat block. The newly created custom block will not show up in the Block Palette. The method can be found in the undefined blocks article.

More of the example tricks used with the NAK (shift in) characters are:

  • No text costumes and sounds
  • Variables remaining even if removed
  • Variables showing "i" and "j"
The variable was removed but remains there in the stage.
No text sound normally won't happen. Though this can also be made by the ZWJ (Zero-width-joiner) and ZWNJ (Zero-width-non-joiner).
The costume editor also glitches.
The stack blocks disappeared.

Backdrop and costumes bug

When uploading a GIF for the backdrop, the frames will be ordered wrong. This glitch also occurs for sprites inside the Costumes tab, but not when uploading outside of it by adding a sprite. Uploading a GIF as a backdrop will also order the frames wrong, even outside of the Costumes tab.[7]

Half Blocks

Putting no name in a block, or putting an ASCII character into a custom block and then removing it after creation will create a "Half block"[8] (it looks like half of a block).

Key pressed glitch

Sometimes, the script editor will say one pressed a key, but they did not.[citation needed] This has not been seen many times, but cannot be considered "fixed" yet due to its appearance.

APNG glitch

Uploading an APNG will not get frames out like GIF.[9]

Question mark glitch

Some emojis or special characters put into the Instructions or Notes and Credits of a project will generate a question mark.

Sans Serif bug

Sans Serif will appear like Serif in the stage selector. However, it won't mess around with anything with the project.

Text too long bug

If one puts a string that is too long in a block, the rest of the text outside the page will be on a purple background. This might not be classified as a "bug" or "glitch".[citation needed]

Mailbox delay bug

Sometimes, even if the message is read, it will show as not read.[10] This often happens while visiting 3.0-style pages such as the homepage.[11]

Upload bug

The Chrome logo disappeared.

If one uploads an animated SVG, the animation will be visible in the sprites selector, but not on the Stage.[citation needed] SVG can also cause problems like being a question mark with a box, the SVG moving to somewhere else and other problems.[citation needed]

403 Forbidden bug

scratch:explorea (anything after explore) will return 403 Forbidden, not 404 Not Found. This is caused by the Fastly configuration.[citation needed]

Blurry blocks bug

On Chromium-based browsers, the blocks on the online editor become blurry when they are running. The cause for this bug is unknown, but it has been reported since October 2021 and seems to be happening only in Chromium-based browsers.[12]

Photo of blurry scratch blocks

Inaccurate studio creation date bug

DocumentInQuestion.png This page or section is in question as to whether it is useful or not. You can discuss whether you think it should be deleted or not on its talk page. (May 2024)
Reason: Studio creation dates in My Stuff are ordered with the DD/MM/YYYY format, so they are most likely correct.

For an unknown reason, and very rarely, sometimes the "created" in the studios section of the My Stuff page will show dates that are incorrect, or show dates that do not exist.[citation needed]

An incorrect date.

Ctrl-Z bug

A bug frequently reported to take place in the paint and code editor, when pressing Ctrl-Z on Windows or Command-Z on Mac (a common "undo" shortcut), instead of the last edit to be undone, it would undo the last action done to any text box instead (i.e. the project title, sprite name, costume name, etc.). The bug is caused by the web browser and Scratch's undo shortcuts interfering with each other.[citation needed] This bug appears to happen only on Chromium-based browsers.[13][14]

Null color input bug

If one drags a reporter block inside of a color input, and then presses undo, the color input will turn into a "null input".

Server Load Issues

SVG Clock.svg
This article or section documents a current event. Information may change rapidly as the event progresses, and this article or section may not reflect the most recent developments on the current version of Scratch, the Scratch Website, or the article or section's subject. If you are an editor, you can help by updating this article or section. (May 2024)
Scratch front page with no projects
The bug as of May 10, 2024

As of 10th May 2024, users will sometimes find data missing from certain pages. While this issue has been prevalent with Scratch 2.0-style pages,[15] such as projects on my stuff,[16] parts of the students tab on classes,[17] profile pages (sometimes just comments),[18] and My Stuff Page,[19] it can also happen with 3.0-style pages, such as the Messages[20] and the Front Page.[21]

Sometimes images don't show up,[22] such as icons on the statistics page, icons for BBCode,[23] project thumbnails[24] and the ScratchBlocks plugin.[25]

Some actions will fail sometimes[26], such as making classes[27], changing About Me, What I'm Working On, and the Featured Project, forum qoutes[28]. Additionally, 503 errors may occur[29], and pages may load slow.

These bugs happen because of Scratch's site capacity limits being exceeded, causing data and images to not be returned. As of 25th April 2024, the Scratch Team is working on fixing it.[30]

Fixed Bugs

Disabled Keyboard Bug

This bug, seen only in Scratch 2.0, caused Scratch to not react to key presses, which impacted projects that needed key presses to work and meant that Scratchers could not program, due to most blocks needing to have words typed in them to work correctly. This bug was only seen with Firefox. There were, at the time, no ways to fix it forever, but it had been found that clicking outside Scratch (such as address bar) fixed it temporarily.[citation needed]

Semicolon Glitch

Main article: Semicolon Glitch

The Semicolon Glitch was a bug that caused a semicolon to be displayed at the bottom left of each page. It has since been fixed, but it has been brought back a few times on April Fools' Day.

Disappearing Text Bug

Main article: Disappearing Text Bug
The bug, shown in a project.

The Disappearing Text Bug was that text in some projects would disappear. It was seen in blocks with written text inside or dropdown menus. In some cases, only some text would disappear, but sometimes, almost all the text in the project would disappear.[31] It has been fixed, and although it was reported to have appeared again in Scratch 2.0, it hasn't been seen for a few years.[32]

Variables Not Fully Hiding

In Scratch 2.0, sometimes, variables did not completely disappear from the Stage when hidden via the checkbox next to its name. The exact cause is uncertain, but it is speculated that quickly switching costumes or backdrops caused it.[citation needed]

White Text

In Scratch 2.0, in Firefox, the project website was loaded with black text appearing white. The cause was unknown, but it might have had to do with the Disabled Keyboard Bug.[citation needed]

Speech Bubbles With Empty Space at the Bottom

Sometimes, there was extra space at the bottom of a speech bubble.

ln Scratch 2.0, when changing to fullscreen, the outside of a speech bubble got amplified the correct amount, but the text appeared a bit smaller relative to the bubble. The result was that the speech bubble was a bit taller than it was supposed to be. This only happened with speech bubbles with lots of text, or large speech bubbles.

Broken Thumbnails and Profile Pictures

Main article: Broken Thumbnail and Profile Picture Bug

As of June 2021, profile pictures and featured project thumbnails stopped showing. There were numerous posts about this on the forums. The bug started due to one of Scratch's subdomains, cdn2.scratch.mit.edu, being down. The downtime lasted 2 days, with any users trying to access images stored in it either getting a 500 Error, or getting a Guru Mediation error[33]. After that time, the downtime stopped, however, the bug continued. After the downtime, many images were corrupted, so many images still could not load. It is suspected that Fastly being down has caused the CDN2 servers to wobble. During the downtime, many people attempting to change their profile pictures got them reset to the default Scratch Cat icon.[34]

\b bug

Including the text '\b' anywhere in the editor used to corrupt the project, disallowing the editor to save the project.[35] When downloaded and uploaded to Scratch, the project used to 'fail to load'. This was fixed on December 14, 2022.[36]

Hide and show glitch

Sometimes, when using the stack blocks to hide and show variables, the checkbox was still there saying showing/hiding.[37]


  1. venyanwarrior. (17/5/2018). "The bug was seen almost every day in the week before May 18th, 2017, where multiple spammers were active." topic:301611
  2. Paddle2See. (2/4/2017). "That's my theory as well - that the "missing" posts were either deleted (moved to the Dustbin sub-forum) or identified as commercial spam (moved to the Spam Dustbin sub-forum)." https://web.archive.org/web/20200508010821/https://i.cubeupload.com/kM3ksD.png
  3. p-p-p-p-p-p-p-p-p-p-. (8/9/2020). "So, in the create block section I click "create block" And then I add a % sign in the label. Then, I add a () and the block goes empty. Then I click okay, and I X the tab out. In the blocks, there is nothing. I scroll up, and there is a huge disaster of blocks." topic:437821
  4. Chiroyce. (29/6/2021). "Yeah this is a known bug, it sends back a malformed cookie that logs you out, also happens with https://scratch.mit.edu/abouta" post:5382167
  5. A project thumbnail like this project thumbnail is not the same image as the real project
  6. Chiroyce (6/11/2021). "Some project thumbnails have turned into Scratch Cat on a white background, and it still happens sometimes, unpredictably." topic:520710
  7. BrycedTea. (10/6/2020). "Uploading gifs as costumes imports images in wrong order [title]" https://github.com/scratchfoundation/scratch-gui/issues/5875
  8. GAMS2. (9/2/2022). "Half block (???) Glitch [title]" topic:578882
  9. raimondious. (14/3/2022). "Importing an animated PNG only imports the first frame of the animation" https://github.com/scratchfoundation/scratch-gui/issues/8097
  10. Eagle138. (24/8/2021). "Messages icon still displays unread messages after I check them [title]" topic:538801
  11. amazingscratchcoder. (25/8/2021). "Even the 2.0 pages are fine but 3.0 bugged it" post:5556614
  12. medians. (22/10/2021). "So, if you're experiencing Blurry Block Glitches where the blocks in the editor are blurry, this is a Chrome/Chromium and Firefox bug." post:5806319
  13. https://github.com/scratchfoundation/scratch-gui/issues/3971
  14. https://github.com/scratchfoundation/scratch-gui/issues/6302
  15. topic:756895
  16. topic:756030
  17. topic:756678
  18. projects:1004853333#comments-399780026
  19. topic:756282
  20. post:7942020
  21. topic:760200
  22. topic:756895
  23. post:7683410
  24. ,post:7939894
  25. post:7939583
  26. post:7940990
  27. topic:756738
  28. post:7937174
  29. post:7940194
  30. post:7940952
  31. ar-topic:21219
  32. topic:114
  33. post:5328230
  34. Chiroyce (6/11/2021). "Some people are not able to change their profile pictures, and some profile pictures have turned into the default scratch cat silhouette, which is a huge problem, and it still happens sometimes, unpredictably." topic:520710
  35. topic:354435
  36. https://github.com/scratchfoundation/scratch-parser/pull/62
  37. https://github.com/scratchfoundation/scratch-gui/pull/4147
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