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Clean HTML for Substack

Substack newsletters are delivered as email, where bloated HTML over 100KB triggers spam filters. Publish Helper reduces HTML size by 50-70% by stripping Google Docs formatting, improving deliverability.

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HTML Issues with Substack

Substack's editor converts paste into its own format but may preserve unwanted inline styles from Google Docs, especially font-family and font-size declarations that override Substack's newsletter typography. Email delivery adds another layer — bloated HTML can trigger spam filters or render poorly in email clients.

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How to Paste Clean HTML into Substack

  1. 1.

    Copy your content from Google Docs, Word, or any editor

  2. 2.

    Paste into Publish Helper and click 'Clean HTML'

  3. 3.

    Copy the clean HTML from Publish Helper

  4. 4.

    Paste directly into Substack's editor

  5. 5.

    Preview your post and send a test email to verify formatting

Clean HTML for Substack
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Substack Tips

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Frequently Asked Questions

Why does my Substack email look different from the web post?

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Email clients render HTML differently from web browsers. Inline styles from Google Docs can cause inconsistencies between Substack's web view and the email version. Clean HTML renders more consistently across both.

Does dirty HTML affect email deliverability?

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Bloated HTML can increase email size and trigger spam filters. Clean HTML from Publish Helper reduces email weight, which helps with deliverability and load times in email clients.

Can I preserve my Google Docs formatting on Substack?

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Substack has its own typography that you should lean into. Instead of trying to preserve Google Docs formatting, clean it with Publish Helper and let Substack's styles handle the presentation.

Last updated: May 2026|Built by content editors for content editors|Used by 10,000+ bloggers
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Last updated: March 2026

Changelog

v3.3.12026-06-17
  • FixSlug generator updated to latest AI model for better reliability
  • FixHeading conversion now supports U+FE30 colon separator (︰) used in vertical CJK text
  • FixHeading conversion no longer includes leading   in the extracted title
  • FixOG image generator now wraps long CJK text and prevents overflow with ellipsis truncation
  • ImprovedUpdated sharp to 0.35.1 for better image processing
v3.3.02026-05-30
  • FixSEO & a11y: <html lang> attribute, theme-color meta, OG image alt text i18n
  • FixGA scripts properly removed on consent decline
  • FixContent Stats i18n + link count regex fix
  • FixTool page section numbering corrected (all 14 pages)
  • ImprovedSimplified cleanup options — removed 10 checkboxes Tiptap already handles, kept only 4 useful ones
  • ImprovedAuto-clean only triggers on paste, not every content change
v3.2.12026-05-26
  • FixHeading converter now correctly splits paragraphs containing MULTIPLE heading-strong elements
  • FixHeading converter now places extracted headings BEFORE their body paragraph instead of after
  • FixEditor toolbar no longer causes React hydration mismatch on first paint
  • FixMissing @tiptap/extension-drag-handle-react dependency added
v3.2.02026-05-23
  • New6 new SEO content editing tools — Case Converter, Text Extractor, Text Diff Checker, Keyword Density Analyzer, SERP Preview Generator, Readability Checker
  • NewHeading dropdown expanded to H5-H6 (was H1-H4 only)
  • NewTable toolbar — insert/delete rows & columns, merge/split cells, toggle header row
  • NewDrag Handle React — drag and reorder blocks in the editor
  • NewCase Converter — 11 case formats including camelCase, PascalCase, snake_case, kebab-case
  • ImprovedSERP Preview — accurate Google-style preview with desktop/mobile views
  • ImprovedText Diff — word-level highlighting within changed lines
  • ImprovedAll new tools linked from the main page TOOLS & GUIDES section and related pages
  • Improvedzh-TW FAQ alignment fixed across all tools
v3.1.12026-05-23
  • FixEditor draft restore — saved content now correctly loads into the Tiptap editor on page reload
  • ImprovedDependency updates for better performance and stability
v3.1.02026-05-14
  • NewBold List Labels — auto-bold label prefixes (e.g. "Name: John" → "<strong>Name:</strong> John") in list items
  • NewFormatting Add-ons group — Heading Conversion, CJK Auto-Spacing, and Bold List Labels now grouped under a collapsible section
  • FixCJK Auto-Spacing now works across HTML tag boundaries
v3.0.22026-05-08
  • FixHeading converter now correctly splits multiple H2/H3 prefixes inside a single <strong> element separated by <br> tags
v3.0.12026-05-07
  • FixHTML cleaner now properly strips orphaned <strong><br><br></strong> tags left behind by Google Docs
  • FixHeading converter now detects H2/H3 prefixes inside <strong> tags embedded at the end of a paragraph
  • FixTrailing <br> tags at the end of paragraphs are now stripped — no more pointless line breaks before headings
v3.0.02026-05-03
  • NewHTML Diff Viewer — compare before and after HTML with a visual diff (green/red)
  • NewContent Stats Calculator — word count, reading time, heading, image, and link counts
  • NewHTML Accessibility Checker — detect missing alt text, empty headings, skipped levels, and more
  • NewOG Image Generator — create 1200×630 social share images from your blog post title
  • NewMarkdown ↔ HTML Converter — bidirectional conversion between Markdown and HTML
  • NewTable of Contents Generator — auto-generate nested TOC from heading tags in HTML or Markdown
  • NewJSON-LD Structured Data Builder — generate Article, BlogPosting, and FAQPage schema markup
  • NewAuto-clean on paste — optional toggle that auto-triggers cleanup when content is pasted
  • NewTable cleanup options — strip cell widths and remove empty table cells
  • NewAuto-save draft — content is saved to localStorage and restored on accidental refresh
  • NewAll new tools linked from the main page TOOLS & GUIDES section and related pages
v2.4.12026-04-27
  • NewParagraph option added to heading dropdown — convert headings back to normal text
  • FixH1–H6 heading prefixes now convert correctly even when pasted with leading line breaks
  • FixFixed page crash on load — cookie consent now renders reliably
  • ImprovedDependency updates for better performance and stability
v2.4.02026-04-17
  • NewClear button — quickly wipe all editor content and reset the HTML panel from the left panel header
  • FixEmpty <p></p> placeholder no longer appears in the HTML panel after clearing the editor
  • NewImage insert via URL — paste any image URL into the editor with a new toolbar popover
v2.3.22026-04-14
  • FixHeading conversion rewritten with DOM parsing — now works with any wrapper tag, split headings, and safely preserves <li> inside lists
  • FixEmpty heading tags left behind by Google Docs are now automatically removed
v2.3.12026-03-25
  • FixHeading conversion now handles spaces before the colon (e.g. "H2 : Title")
  • FixRight-to-left content (Arabic, Hebrew) no longer inverts embedded English text in the editor
  • FixSpacer paragraphs (&nbsp;) are now preserved in the HTML output instead of being stripped
v2.3.02026-03-20
  • NewCJK auto-spacing — automatically insert spaces between CJK characters and English letters or numbers (powered by pangu.js)
  • NewStandalone CJK Auto-Spacing tool page with before/after examples, FAQ, and SEO-optimized bilingual content
  • NewChinese UI text auto-spacing — zh-TW interface text now has proper CJK–Latin spacing
  • FixMobile toolbar no longer floats and follows scrolling — stays pinned at the bottom of the editor
  • FixMobile toolbar buttons now scroll horizontally instead of overflowing
  • FixFind & Replace inputs no longer break out of the container on narrow screens
v2.2.12026-03-20
  • FixHeading conversion now uses the text prefix (e.g. H3:) to set the heading level, even when the content is already inside a different heading tag
v2.2.02026-03-18
  • NewAI-Powered Title to SEO Slug — Convert blog titles in any language to SEO-friendly English slugs in under 10 seconds
  • NewSlug generator toggle on the main page — generate slugs right after editing, above the fold
  • NewTable support — pasted tables from Google Docs now render correctly
  • NewRemove <br> after headings cleanup option (on by default)
  • NewPartial text selection copy in the HTML code view
  • NewSticky Clean HTML button at the bottom of the page
  • ImprovedHeading conversion now strips prefixes from existing heading tags and supports Chinese full-width colon (：)
  • ImprovedShared footer across all pages
v2.1.22026-03-17
  • FixBug fixes and improvements
v2.1.12026-03-16
  • FixBug fixes and improvements
v2.1.02026-03-16
  • NewFormatted/Raw toggle for the HTML code view
  • ImprovedCopying from the code panel now always gives clean, unformatted HTML
v2.0.02026-03-16
  • NewWelcome to Publish Helper — free online tools for content editors
  • ImprovedImproved search engine visibility
v1.1.02026-03-16
  • ImprovedClipboard copy — clean HTML output matches the code view
v1.0.02026-03-16
  • NewRich text editor with Google Docs paste support
  • NewHTML cleanup: strip styles, classes, empty tags, and Google Docs artifacts
  • NewHeading conversion from text prefixes to proper HTML tags
  • NewFind & replace with regex support and saveable presets
  • NewSyntax-highlighted HTML preview with one-click copy
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