The Mystery of the Triple Header: Unraveling a Hidden Shopify Liquid Code Bug

View original discussion by CW5 on Shopify Community →

Hey everyone! As a Shopify migration expert and community analyst, I spend a lot of time sifting through forum discussions, and every now and then, a thread pops up that’s just too good (and too frustrating!) not to share. It's the kind of head-scratcher that makes you want to pull your hair out, but the solution, once found, is a brilliant lesson for us all.

Recently, a store owner, CW5, brought a truly perplexing issue to the Shopify Community: their static "Header" section was rendering three times sitewide after a custom mega-menu rebuild. This wasn't just a visual glitch; it was tripling the page's HTML weight and creating invalid duplicate element IDs. Shopify Support, understandably, confirmed it was out of scope for a heavily customized theme, leaving CW5 to debug a truly thorny problem.

The Great Header Hunt: Ruling Out the Usual Suspects

CW5's initial investigation was thorough. They checked for duplicate {% section 'header' %} calls across all layout files (even obscure ones like theme.aftership.liquid), systematically disabled apps, cleared editor caches, and even tested reducing the number of blocks and block types in the header's schema. Nothing. The problem persisted, showing three identical "Header" entries in the Theme Editor and in the raw HTML, despite only one call in the code.

Community members like Mustafa_Ali and Fridaous jumped in with excellent suggestions, focusing on common culprits in Shopify Online Store 2.0 themes:

  • Section Group JSON Conflicts: Checking for a header-group.json file or multiple references to the header section within a section group.
  • Nested {% section %} Tags: Looking for accidental {% section 'header' %} calls hidden inside snippets instead of {% render %}.
  • settings_data.json Orphan Mappings: Investigating duplicated section instance definitions.

CW5 diligently checked all these avenues, providing detailed updates, but each time, the answer was the same: ruled out. The problem wasn't in these common areas, and the mystery deepened.

The "Aha!" Moment: HTML in CSS Comments?

Then came a pivotal moment thanks to community member Ploqo. After examining CW5's store (curatedwines.sg), Ploqo made a crucial observation: while "view source" showed three headers, the actual live DOM (what the browser renders) only showed one. Two of the "extra" copies were found sitting inside CSS comments within the custom CSS!

Here's how Ploqo illustrated it:

Two of the three are header markup pasted into CSS comments

Ploqo's theory was that the browser simply ignored the HTML within comments, explaining why only one header was truly rendered. This was a fantastic lead, and CW5 confirmed that the raw HTML indeed showed two copies genuinely positioned inside a