Previews

See a post the way each network will show it before it goes out: locally while you write, and on every pull request.

#postline preview

postline preview --open

This starts a page on http://127.0.0.1:4400 with every post and, for each one:

• the rendered card;
• lint results;
• one panel per channel with the exact text that channel gets (including variants:), its length against that network's limit, and links and hashtags highlighted the way the network shows them;
• for LinkedIn, roughly where the post cuts off behind "…see more" (about 210 characters), so the hook lands above it;
• characters past a network's limit, struck through;
• for webhooks, the JSON payload; for the files channel, the Markdown file it writes.

The page reloads when you save a post, the config or a design file. It only listens on localhost. --port picks another port.

The network panels are close approximations, not screenshots: each network changes its layout often, and the fold position varies with screen width.

#Pull request previews

The postline GitHub Action comments on every pull request that changes posts: the rendered card, lengths per channel, lint results and the post text. One comment per project, updated on every push.

Projects made with postline init already use it. To add it to an existing workflow:

on:
  pull_request:

jobs:
  check:
    runs-on: ubuntu-latest
    permissions:
      contents: write        # pushes card images to the postline-previews branch
      pull-requests: write   # comments on the pull request
    steps:
      - uses: actions/checkout@v4
      - uses: 1cbyc/postline@v0.3.2
        with:
          fail-on-error: "true"     # fail the check when a changed post has lint errors
          # working-directory: marketing   # where postline.config.yaml lives

How it works:

• Only posts the pull request adds or changes are shown in full. Lint errors in other posts are listed in one line and still fail the check with fail-on-error, because they block publishing.
• Changes are measured from where the branch left the base branch, so posts changed on main in the meantime don't show up.
• If the config, design tokens, stylesheet, a custom layout or the logo changes, every card may look different, so all posts are shown (the first 12 in full).
• GitHub comments can only show images from a URL, so the cards are pushed to a postline-previews branch and the comment links to them. That branch only holds preview images and can be deleted at any time.
• On pull requests from forks the token can't push or comment, so the report goes to the job summary instead.
• On private repositories GitHub may not display the images inside the comment. The lint results and post text still appear, and the cards are in the postline-previews branch.

The same report is available on the command line:

postline pr-report --base origin/main            # posts changed since main
postline pr-report --all --images out/pr         # every post, with rendered cards