The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →A standard HTML/CSS to Image API request that returns 401 Unauthorized usually has an incorrect API ID/API key pair or a disabled key. The standard API uses HTTP Basic authentication: the API ID is the username and the API key is the password. If you are generating a signed image URL instead, check its HMAC SHA-256 token against the exact query string. A 403 Forbidden generally points to permissions or plan eligibility, not failed authentication.
First identify which authentication path you use
HTML/CSS to Image has two relevant request patterns. Diagnose the one in your request rather than changing credentials or code at random.
| Request type | Authentication | First 401 check |
|---|---|---|
Standard image creation, POST https://hcti.io/v1/image |
HTTP Basic: API ID as username and API key as password | Confirm the matching credential pair and that the key is enabled. |
| Signed create-and-render URL | HMAC SHA-256 token generated from the query string, using the API key as the secret | Recompute the token from the exact query string and confirm the signing key is enabled and has images:create. |
Fix a 401 on a standard API request
- Check the API ID and API key together. Make sure both values belong to the same key and intended organization. A correct-looking ID paired with a key from another account will not authenticate.
- Confirm that the key is enabled. Review the key controls in your HTML/CSS to Image account. A disabled key cannot authenticate.
- Inspect how the client constructs Basic authentication. The server-side JavaScript example from the vendor constructs the Authorization value from
API_ID:API_KEY, Base64-encoded. Use the authentication mechanism supported by your HTTP client, and make sure the values are not being altered or truncated. - Retry with the corrected credentials. If the response remains 401, use the response body and the actual outgoing request to narrow down what is still wrong. A 401 does not establish that every client library failed for the same reason.
Keep the key in protected server configuration or environment variables. The vendor’s API guide puts it plainly: “Treat your API Key like a password.” Do not put it in browser-side JavaScript, public repositories, screenshots, or support messages.
Fix a 401 on a signed image URL
Signed URL authentication is different from Basic authentication. The token is an HMAC SHA-256 hash of the query string without its leading ?, with the API key as the secret. Check these details together:
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- Sign the exact query string used in the URL, excluding only the initial question mark.
- Preserve parameter order, encoding style, and whitespace. Changing any of them after signing changes the input and invalidates the token.
- Use the API key as the HMAC secret, and verify that the key is enabled.
- Confirm that the key grants the
images:createpermission required for signed image generation.
If a URL has been rewritten by a client, proxy, template, or manual edit, rebuild the URL and recompute its signature from the final query string rather than reusing the old token.
Know when the error is 403, not 401
HTML/CSS to Image distinguishes authentication from authorization: missing or invalid credentials return 401, while valid credentials without the required permission return 403. For a 403, check the permission named in the response, confirm the key belongs to the organization that owns the resource, and verify that your plan allows the operation. A permission grant does not necessarily override a plan restriction.
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Common failure checks
- 401 immediately after rotating credentials: verify the application is using the new, matching API ID and key, not a stale environment value; confirm the key is enabled.
- Standard API request works locally but fails in deployment: compare the deployed credential values and authentication construction with the working request, without logging or exposing the secret.
- Signed URL fails after a parameter change: regenerate the signature after the final query string is assembled, preserving its exact order and encoding.
- Request returns 403: stop treating it as a bad-password problem; inspect the permission and plan eligibility for the requested operation.
If these checks do not resolve the specific failure, HTML/CSS to Image lists [email protected] for API key assistance. Share the status, response details, and a redacted request example, never the secret key itself.
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If your goal is simply to capture a webpage as an image or PDF, ScreenshotNeo offers a separate screenshot API with a one-request flow. Its API accepts a URL and returns a screenshot or PDF; documentation: ScreenshotNeo API docs.
Quick Recap
Best Value
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- POWERFUL SECURITY KEY: The Security Key NFC is the essential physical passkey for protecting your digital life from phishing attacks. It ensures only you can access your accounts.
- WORKS WITH 1000+ ACCOUNTS: Compatible with Google, Microsoft, and Apple. A single Security Key NFC secures 100 of your favorite accounts, including email, password managers, and more.
- FAST & CONVENIENT LOGIN: Plug in your Security Key NFC via USB-A and tap it, or tap it against your phone (NFC) to authenticate. No batteries, no internet connection, and no extra fees required.
- TRUSTED PASSKEY TECHNOLOGY: Uses the latest passkey standards (FIDO2/WebAuthn & FIDO U2F) but does not support One-Time Passwords. For complex needs, check out the YubiKey 5 Series.
- BUILT TO LAST: Made from tough, waterproof, and crush-resistant materials. Manufactured in Sweden and programmed in the USA with the highest security standards.
Rank #3
- POWERFUL SECURITY KEY: The YubiKey 5 NFC is the most versatile physical passkey, protecting your digital life from phishing attacks. It ensures only you can access your accounts
- WORKS WITH 1000+ ACCOUNTS: Compatible with popular accounts like Google, Microsoft, and Apple. A single YubiKey 5 NFC secures 100+ of your favorite accounts, including email, password managers, and more
- FAST & CONVENIENT LOGIN: Plug in your YubiKey 5 NFC via USB and tap it, or tap it against your phone (NFC), to authenticate. No batteries, no internet connection, and no extra fees required
- MOST SECURE PASSKEY: Supports FIDO2/WebAuthn, FIDO U2F, Yubico OTP, OATH-TOTP/HOTP, Smart card (PIV), and OpenPGP. That means it’s versatile, working almost anywhere you need it
- PRIMARY & SPARE KEYS: Just like having a spare house key, we recommend buying two YubiKeys - one for daily use and one as a spare. That way you’ll never get locked out of your accounts
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