Like you see in inspector, you defined only border color but not border width. Because it is 0px, it is invisible ;)

You need to change it to

class="border border-gray-800"

"border" will by default mean border-width: 1px so if you need thicker use for example

class="border-2 border-gray-800"

or if you wanna it only on one side

class="border-right border-gray-800"

More in documentation.

Answer from chojnicki on Stack Overflow
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Tailwind CSS
tailwindcss.com › docs › border-collapse
border-collapse - Tables - Tailwind CSS
<table class="border-collapse border border-gray-400 ..."> <thead> <tr> <th class="border border-gray-300 ...">State</th> <th class="border border-gray-300 ...">City</th> </tr> </thead> <tbody> <tr> <td class="border border-gray-300 ...">Indiana</td> <td class="border border-gray-300 ...">Indianapolis</td> </tr> <tr> <td class="border border-gray-300 ...">Ohio</td> <td class="border border-gray-300 ...">Columbus</td> </tr> <tr> <td class="border border-gray-300 ...">Michigan</td> <td class="border border-gray-300 ...">Detroit</td> </tr> </tbody></table> Note that this includes collapsing borders on the top-level <table> tag.
Discussions

Border won't show up
Border is overriding border-2 and solid is default, it’s used for breakpoint changes. All you need is border-2 and border-indigo-600 Don’t sweat the style sheet, it’s generated by your classes. More on reddit.com
🌐 r/tailwindcss
6
1
August 22, 2023
forms.py isnt applying tailwind styles
I am building an app using django-tailwind. Everything is working and going good. However, I just started creating the login page and when I went to style the inputs via forms.py no style or settings is being applied. Per django-tailwind instructions I create an app called “theme”. I have ... More on forum.djangoproject.com
🌐 forum.djangoproject.com
0
September 7, 2024
Tailwind not loading all styles : Forums : PythonAnywhere
The above properly displays the ... the border weights etc. The only classes that seem to be loading for Tailwind are the alignment/page layout and the text colors. None of the bg-background colors work for any element, and there don't appear to be any log/error notes/console outputs ... More on pythonanywhere.com
🌐 pythonanywhere.com
Tailwind border styles don't apply
Duplicates I have searched the existing issues Latest version I have tested the latest version Steps to reproduce 🕹 Link to live example from official tailwind+mui example: https://codesandbox.io/s... More on github.com
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9
May 22, 2023
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GitHub
github.com › tailwindlabs › tailwindcss › issues › 10552
Issue with border color not overriding · Issue #10552 · tailwindlabs/tailwindcss
February 10, 2023 - https://github.com/jiblett1000/tailwind-classes · Describe your issue · Hello, Something in either 3.2.5 or 3.2.6 has messed up class cascading for border colors. The other border classes seem to be ok, but there could be other classes affected as well, idk. When using something such as someVar && "overrideClass", it will not override any previous border color on that tag, component, etc.
Published   Feb 10, 2023
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Reddit
reddit.com › r/tailwindcss › border won't show up
r/tailwindcss on Reddit: Border won't show up
August 22, 2023 -

I'm a beginner to Tailwind, so it's likely something simple. I can see an <input type="text" class="border border-solid border-2 border-indigo-600">, but only a faint 1px border of #e5e7eb shows up. I can see that this is under the *, ::before, ::after rule at the top of the stylesheet. My config file is customized only for the content paths, and theme and extend are empty. I read quite a bit of the Tailwind documentation, but I'm having a lot of trouble wrapping my head around how basics like color intersect with border, background, and text seeing as the latter three all incorporate color.

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Tailwind CSS
v3.tailwindcss.com › docs › border-radius
Border Radius - Tailwind CSS
You can change, add, or remove these by editing the theme.borderRadius section of your Tailwind config.
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GitHub
github.com › tailwindlabs › tailwindcss › discussions › 16002
Using @layer base { border-color } is not working for TailwindCSS ver 4 · tailwindlabs/tailwindcss · Discussion #16002
My custom border-sidebar-accent just gets overwritten by the gray-200 value :( Do you have a solution? Beta Was this translation helpful? Give feedback. ... There was an error while loading. Please reload this page. Something went wrong. There was an error while loading. Please reload this page. ... @import "tailwindcss/theme"; @layer base { :root { color-scheme: light dark; } *, ::after, ::before, ::backdrop, ::file-selector-button { border-color: var(--color-gray-200, currentColor); } } @theme { --color-background: var(--wp--preset--color--background); --color-foreground: var(--wp--preset--c
Author   tailwindlabs
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Kombai
kombai.com › tailwind › box-sizing
Tailwind CSS Box Sizing
By default, elements use content-box, which only includes the content's dimensions. Switching to border-box means padding and border are included in the total size. In Tailwind CSS, box-sizing utilities allow developers to control how box dimensions are derived with minimal effort.
Find elsewhere
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Tailwind CSS
tailwindcss.com › docs › border-style
border-style - Borders - Tailwind CSS
Use utilities like border-solid and border-dotted to control an element's border style:
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Django Forum
forum.djangoproject.com › using django › templates & frontend
forms.py isnt applying tailwind styles - Templates & Frontend - Django Forum
September 7, 2024 - I am building an app using django-tailwind. Everything is working and going good. However, I just started creating the login page and when I went to style the inputs via forms.py no style or settings is being applied. Per django-tailwind instructions I create an app called “theme”. I have ...
🌐
PythonAnywhere
pythonanywhere.com › forums › topic › 34616
Tailwind not loading all styles : Forums : PythonAnywhere
The above properly displays the ... the border weights etc. The only classes that seem to be loading for Tailwind are the alignment/page layout and the text colors. None of the bg-background colors work for any element, and there don't appear to be any log/error notes/console outputs ...
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Tailwind CSS
tailwindcss.com › docs › compatibility
Compatibility - Getting started - Tailwind CSS
If you're using Tailwind with these tools, we recommend avoiding <style> blocks in your components and just styling things with utility classes directly in your markup, the way Tailwind is meant to be used. If you do use <style> blocks, make sure to import your global styles as reference if you want features like @apply to work as expected:
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Shuffle
shuffle.dev › tailwind › classes › border-color › border-green-700
Tailwind CSS class: border-green-700
Tailwind CSS class border-green-700 with source code and live preview. You can copy the example and paste it into your project or use the Shuffle editor and not write code by hand!
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GitHub
github.com › mui › material-ui › issues › 37371
Tailwind border styles don't apply · Issue #37371 · mui/material-ui
May 22, 2023 - Link to live example from official tailwind+mui example: https://codesandbox.io/s/react-tailwind-borders-issue-xmig8s?file=/src/App.tsx For some reason tailwind border styles don't work.
Published   May 22, 2023
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GitHub
github.com › tailwindlabs › tailwindcss › issues › 1167
Borders not visible with disabled preflight · Issue #1167 · tailwindlabs/tailwindcss
August 17, 2019 - I try to use tailwind in an existing project and therefore I disable Preflight in my tailwind.config.js corePlugins: { preflight: false, } But then it seems that the border classes don't seem to work. I don't know if it also affects othe...
Published   Oct 16, 2019
🌐
GeeksforGeeks
geeksforgeeks.org › css › border-style-not-working-on-hover-in-tailwind-css
Border Style Not Working on Hover in Tailwind CSS? - GeeksforGeeks
July 23, 2025 - </button> </body> </html> ... In Tailwind CSS, it is very important to apply the hover class with the correct structure. If we place the hover: class in the wrong place, it will not work.