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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallUnknown, missing, or boxed characters in a Wicked PDF document usually have one of three causes: the Rails input is already mis-decoded, the HTML does not declare UTF-8, or wkhtmltopdf cannot find a font glyph for the character. Header and footer text can fail independently of the body. Diagnose those paths separately instead of adding more encoding flags at random.
How Wicked PDF produces the PDF
Wicked PDF is a Rails wrapper around the wkhtmltopdf command-line renderer. Your text passes through several boundaries:
- Ruby reads a source string or renders a view.
- The view becomes HTML.
- wkhtmltopdf detects or guesses the HTML encoding.
- The renderer selects installed fonts and substitutes glyphs.
- Body, header, and footer content may be rendered through different mechanisms.
A failure at any boundary can look like a generic “Unicode” problem. First identify whether the wrong characters are present in the HTML, absent only in the PDF body, or absent only in a header or footer.
1. Verify the characters before conversion
Inspect the exact string and rendered HTML immediately before Wicked PDF receives it. Test characters that represent your real case, such as ş ğ İ ı ñ é € Ж 中 العربية. If the log, view source, or saved HTML already contains replacement characters (�), question marks, or mojibake such as é, the renderer cannot repair the data.
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Rails checks
- Keep source files saved as UTF-8.
- Check the encoding of strings crossing CSV, database, HTTP, or queue boundaries.
- Do not call an arbitrary
force_encodingunless you have established what the bytes mean; that changes Ruby’s label, not the bytes. - Save the final HTML to a file and inspect it in a UTF-8-aware editor before invoking PDF conversion.
html = render_to_string(template: "invoices/show", formats: [:html], locals: { invoice: @invoice })
Rails.logger.debug(html.encode("UTF-8"))
The debug output is only useful if it is the same HTML passed to the converter. A separately rendered diagnostic view can hide the real failure.
2. Declare UTF-8 in the PDF HTML
Put the declaration inside the document’s <head>, before content that depends on encoding:
<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<%= wicked_pdf_stylesheet_link_tag "pdf" %>
</head>
<body>
<%= @invoice.customer_name %>
</body>
</html>
Wicked PDF’s documented render options also show an explicit UTF-8 encoding value:
render pdf: "invoice",
encoding: "UTF-8",
template: "invoices/show.html.erb"
At the wkhtmltopdf level, web.defaultEncoding is a fallback used when the content does not specify an encoding. It is not a glyph installer and cannot correct bytes that were decoded incorrectly upstream.
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Minimal command-line reproduction
Use a tiny file to remove Rails variables from the test:
wkhtmltopdf --encoding UTF-8 unicode-test.html unicode-test.pdf
Put the same characters and an explicit font family in unicode-test.html. If this works while the application fails, compare the generated HTML, options, and runtime environment rather than changing the text.
3. Distinguish encoding from missing glyphs
UTF-8 tells the renderer which character value it received. A font must still contain a glyph for that value. Boxes, blank squares, or a missing character with otherwise correct accents commonly indicate font coverage or font discovery, not input encoding.
Check the actual rendering environment
- Install the font on the machine, container, VM, or worker that launches wkhtmltopdf—not merely on your development laptop.
- Confirm the configured CSS family name exactly matches an installed family.
- Choose a known glyph-capable fallback for the script you need and test it explicitly.
- Verify that fontconfig and FreeType can discover and load the font under the service account.
- After installing fonts in a container, refresh its font cache and rebuild the image according to that distribution’s packaging rules.
body {
font-family: "Noto Sans", "DejaVu Sans", sans-serif;
}
The example is a diagnostic choice, not a guarantee that either family covers every writing system. Test the exact characters your document contains. A font that handles Turkish may not cover Chinese, emoji, or a specialist symbol.
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Compare two fonts
Render one PDF with your production family and one with a confirmed glyph-supporting family. If only the latter displays the character, the input and encoding path are probably sound and the font installation or fallback chain needs correction.
4. Test body text separately from headers and footers
Wicked PDF headers and footers can be supplied as templates or as wkhtmltopdf command-line text. They are a separate diagnostic path. Put the same character in the body, header, and footer:
- Body fails: start with HTML bytes, the meta declaration, renderer encoding, and fonts.
- Body works but template header/footer fails: inspect that template’s HTML head, stylesheet loading, and font availability.
- Body works but command-line header/footer text fails: reduce the text to a minimal case and test the exact wkhtmltopdf build and invocation. A historical report on Wicked PDF with wkhtmltopdf 0.12.3 on RHEL 7.3 described accented footer text being dropped despite UTF-8 arguments and locale settings.
Do not treat that historical report as a universal defect: it is evidence of a version- and environment-specific failure mode. Moving the text into a UTF-8 header template can be a useful isolation test, but verify the resulting PDF rather than assuming it fixes every build.
5. A repeatable diagnostic checklist
- Record the exact missing characters and whether they are wrong, blank, or displayed as boxes.
- Log or save the final HTML and verify its characters before conversion.
- Add
<meta charset="utf-8" />to the PDF layout. - Pass
encoding: "UTF-8"through Wicked PDF where your render path supports it. - Run a minimal HTML-to-PDF test outside Rails.
- Record the wkhtmltopdf version, operating system, package source, and build.
- Check the selected font, installed files, fontconfig discovery, and FreeType runtime in the production process.
- Compare a known glyph-capable font with the configured family.
- Render body, header, and footer samples independently.
- Open and inspect the produced PDF; a successful process exit does not prove that every glyph is present.
Common symptoms and fixes
| Symptom | Most useful next check | Likely boundary |
|---|---|---|
| Mojibake such as é | Inspect source bytes and decoding before rendering | Application input |
| Every non-ASCII character is wrong | Add the HTML meta declaration and verify the actual HTML encoding | Encoding detection |
| One script appears as boxes | Test a font that contains that script and verify font discovery | Glyph coverage/runtime |
| Body works; footer accents disappear | Test the footer mechanism independently and record the exact build | Header/footer path |
| Works locally, fails in a container | Compare package, fonts, fontconfig, FreeType, user, and locale | Deployment environment |
| Changing encoding flags has no effect | Check whether the input is already corrupted or the font lacks the glyph | Wrong layer being changed |
Version and packaging cautions
The wkhtmltopdf project lists stable series 0.12.6, released June 11, 2020. That date does not establish what your operating system currently installs. Package builds can differ in patched features, bundled libraries, and font behavior. Record the output of wkhtmltopdf --version, identify whether the binary came from a distribution package or a bundled build, and reproduce with the same artifact in production. The project’s issue repository was archived read-only on January 2, 2023, so old issue comments should be treated as historical troubleshooting evidence, not current release guarantees.
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Performance, reliability, and deployment notes
Font discovery and page rendering occur for every conversion process or worker. Keep a deterministic renderer image with fonts installed, and make the same image available to background jobs and web processes. Avoid relying on a developer’s personal fonts or locale. For reliable regression tests, store a small HTML fixture containing the scripts and symbols your product promises to support, render it after dependency changes, and inspect the PDF text and visual output. Test headers and footers as fixtures too.
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Does setting UTF-8 install the missing characters?
No. Encoding identifies character values; the renderer still needs a font containing the corresponding glyphs.
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Why can the body work while the footer fails?
Wicked PDF can render footer content through a separate template or command-line path, so test and configure that path independently.
Should I upgrade wkhtmltopdf first?
Record and compare versions first. The documented stable series is 0.12.6 from June 11, 2020, but a version change alone does not prove whether your bytes, fonts, or footer mechanism caused the failure.
The Bottom Line
Fix the layer that is actually failing: verify the characters in the generated HTML, declare UTF-8, pass the renderer’s UTF-8 option, install and verify a glyph-capable font in the runtime environment, and test headers and footers separately.
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