The plugin generated 3 characters of unexpected output during activation

What is BOM?

The UTF-8 byte order mark or simply UTF-8 BOM is a series of bytes that helps the reader to understand the encoding of the current document.

These 3 bytes are:

EF BB BF

Or simply the Unicode character : U+FEFF

In a plugin file encoded as BOM, these bytes will be output when the template is called, causing early output in header, that triggers a common error:

The plugin generated X characters of unexpected output during
activation.

This can also happen to theme’s files. Since using BOM for UTF-8 files is not recommended by Unicode Standards, you can save your templates as UTF-8 without BOM.

You will also notice that every UTF-8 file that is encoded under BOM has at least a size of 3 bytes, even if it’s empty.

Related Posts:

  1. Conditionally enqueue a widget’s script/stylesheet in HEAD (only when present on page!)
  2. Adding a widget programmatically
  3. Delete Custom Dashboard Widgets
  4. How to pass JavaScript variable to PHP in wordpress widget?
  5. Is dynamic forms/entries possible in Widget?
  6. How To Add an Extra Field in All WordPress Available Widgets?
  7. Using the media uploader in a custom plugin
  8. Has anyone been able to get the aweber plugin to work
  9. How to create a widget or plugin to add custom content to my website?
  10. WordPress widget / plugin….fields not appearing in my widget
  11. Custom Widget outputs the input but doesn’t save anything inside the textarea
  12. How can I retrieve data within my widget
  13. How to Get Admin Settings for a widget when using the_widget() with custom widget
  14. How to unregister a widget from a child theme
  15. WordPress multiple widget in single plugin
  16. Setting up widgets in wordpress with a unique ID for the after_title argument
  17. How to exclude a widget from page 1 of a paginated post
  18. how can i limit the number of instances for my widget
  19. Dashboard Widget Form
  20. I need some direction on how to have a sidebar based on meta rather than page
  21. How can I reuse the WordPress search form for a custom plugin / widget?
  22. Admin Dashboard with Custom Tab for Client
  23. Passing $this->get_field_name() to javascript
  24. Is there plugin to show recent posts from one website in the widget area of another?
  25. Can I use a form in a dashboard widget?
  26. Missing argument 3 for wp_register_sidebar_widget()
  27. The called constructor method for WP_Widget in GFWidget is deprecated since version 4.3.0! Use
  28. I wrote my plugin. How to display the result of the plugin’s function to sidebar (widget?)?
  29. How to check if you are on widget.php page?
  30. How to save additional user data as part of the registration process?
  31. Theme’s default styles are overriding my plugin’s custom CSS
  32. Adding widgets to header and footer from plugin
  33. Archive – same title for the first two posts
  34. Rotate Widgets or Content Blocks every x sec/min
  35. Do widget options need to be escaped widget()?
  36. Ajax contact form widget plugin data not insert in database
  37. How to remove traces from widget during uninstallation
  38. Which widget to use for display category post with view more? [closed]
  39. WordPress Widget Not Saving Data
  40. In the archive widget, how do I sort in between two years?
  41. Wysiwyg editor errors
  42. How to make WordPress customizable for clients
  43. How to get my plug-in, wrote in php, to refresh on its own every 5 minutes?
  44. Conditional tag in Widget Logic for checking if top level page or if subpage
  45. Char limit on custom blog-post form? [closed]
  46. How do I use wp_editor() in widget form?
  47. How to reorder and display a feed to be chronological?
  48. How to add Wrapper Div/container element around WordPress Widget Content
  49. Disabling plugin but wpenqueue is not available
  50. Related posts widget or plugin needed
  51. Problem since update 3.5 [duplicate]
  52. How to disable a widget when dependent plugin is inactive?
  53. Best practice for including plugin output in a template without using shortcode?
  54. How can I delete a wordpress widget instance?
  55. Add Shortcode tag in Widget/Sidebar
  56. How to create wordpress widget that is fixed position on the home page
  57. Saving widget options from class method
  58. How to handle forms from sidebar widgets – Processing $_POST variables using get_field_name()
  59. Short messages widget [closed]
  60. My widget won’t update its values when save is clicked
  61. How to display a widget on a page with no theme?
  62. Widget where it can make changes to the container
  63. Widget content turns up before title
  64. Extend a plugin to include a widget option
  65. Is there a Image Gallery which will load all my posted Images like twitter’s image grid?
  66. Modify pages widget and make a plugin?
  67. wp_footer hook running twice
  68. Is there any plugin to show number of clicks on the link?
  69. Table of contents (TOC) plugin is not showing header tag
  70. co-authors plugin – inline listing
  71. How can I display selected content from a seperate database in an Activity style widget?
  72. RSS Feed on WordPress showing code (hypertext) in articles titles
  73. Change language in SiteOrigin Widgets
  74. Some Widgets in the Right Side Bar and the whole Footer section is not working in a WordPress Site
  75. Using foreach loop for `$instance` of form and update array widget iteration
  76. Shortcode generated widget to appear on same line as heading text and button
  77. How do I keep children of certain parent menus expanded by default on a sidebar?
  78. Registered sidebar area is not shown from plugin.
  79. Widget logic using woocommerce product category
  80. Using slightly modified widget
  81. How to display widget in front end?
  82. Using Widget Logic to place menu on multiple pages?
  83. Plugin Works, but Widget Doesn’t
  84. Widget Script Loads at Bottom of Page
  85. Use of apply_filter in plugin/widget class
  86. jquery conflict with widget page
  87. Plugin: Unable to Save the Image Alignment Option to Display in the Widget in the Sidebar
  88. Template from scratch: Sidebars not showing widget
  89. Widget redirecting to home page
  90. How to use template field in the Event Organiser plugin widget
  91. How to develop an extension for a simple form post and post back? [closed]
  92. How to add homepage Widget?
  93. What can I do to customize a widget provided with this plugin? from where have I to start?
  94. Content expands beyond its column container [closed]
  95. Am having issues intergrating this api into my wordpress site, any help please?
  96. How can I add a zip code service availability checker in WordPress without Woocommerce? [closed]
  97. Use custom Javascript for a custom Elementor Widget [closed]
  98. Hide attributes based on previous selection
  99. WordPress child theme widget customization – Eduma
  100. Widget saving but showing “waiting” animation [closed]