Synapse Inspect

Synapse Inspect is a message quality analysis pipeline. For email, it detects rendering issues, spam triggers, accessibility violations, and dark-mode problems through a multi-stage pipeline. It also inspects push, in-app, SMS, and WhatsApp templates — each with checks tuned to that channel — before you send a campaign, activate a flow, or (for WhatsApp) submit a template to Meta.

Note

For the full API reference, see Inspect API. This page covers the email pipeline in depth; for the other channels see SMS Quality Checks and WhatsApp Pre-Submission Inspect.

Channels

Channel	What Inspect checks	Guide
Email	HTML/CSS/accessibility/size, spam, dark mode, subject & preheader, tracking — up to five stages	This page
Push	NLT rendering, per-platform length, APNs/FCM payload size, deep links	—
In-app	Placement key, NLT rendering, payload size, CTA limits	—
SMS	Segments & encoding (cost), opt-out language, sender number, NLT rendering	SMS Quality Checks
WhatsApp	Meta placeholder rules, body limit, category, NLT rendering (pre-submission)	WhatsApp Pre-Submission Inspect

What It Does

Inspect analyzes your email template HTML through up to five stages:

Stage	Name	What It Checks	Speed
1	Static Analysis	HTML structure, CSS compatibility, accessibility, email size, dark-mode meta tags, spam keywords, subject/preheader, tracking UTMs	< 1s
2	External Resources	Broken links, image format/size/dimensions, CDN performance	< 10s
3	Spam Scoring	Aggregate spam score via internal heuristics or external provider	< 5s
4	Vendor Render	Multi-client rendering screenshots (Gmail, Outlook, Apple Mail, etc.)	< 60s
5	Visual Diff	Cross-client deviation detection via perceptual hashing	< 10s

Quick Check (Stages 1--3 only) is free and fast -- suitable for inline editor use on every save. A Full Inspect (all 5 stages) requires plan-tier credits and includes vendor rendering.

Note

Inspect analyzes the complete email, not just the content fragment. Synapse email templates are content-only — they store the body, not a full HTML document with a <!DOCTYPE>, <meta charset>, <title>, or dark-mode metas. Before the document-structure checks run, Inspect wraps a content-only fragment in a minimal complete document (using the subject and preheader you supply), so structural findings like missing DOCTYPE, charset, lang, and color-scheme metas reflect the email that will actually be delivered rather than the bare fragment. This applies to every template origin — the editor, the API, clones, and version restores alike. To have the subject and preheader checks evaluate correctly, pass subject and preheader on the Inspect run; see the Findings Catalog note on content-only templates. The shipped email itself also now carries color-scheme / supported-color-schemes metas so it renders correctly in dark mode.

When to Use It

Before sending a campaign -- Inspect is integrated into the campaign send flow. If critical findings exist, the send is blocked until you fix them or explicitly override (with audit trail).
Before activating a flow -- Every email step in a flow is checked for critical findings before the flow can go live.
During template editing -- Quick Check runs inline to catch issues early. Full Inspect can be triggered from the editor toolbar.
Via the API -- Programmatic access for CI/CD integration or custom workflows.

Quick Start

1. Trigger an inspect run

bash

curl -X POST https://synapse-api.pyrx.tech/v1/inspect \

-H "X-WORKSPACE-ID: <workspace-id>" \

-H "X-API-KEY: <api-key>" \

-H "Content-Type: application/json" \

-d '{

"template_slug": "welcome-email",

"quick_check": true

2. Check the results

bash

curl https://synapse-api.pyrx.tech/v1/inspect/<job-id>/findings \

-H "X-WORKSPACE-ID: <workspace-id>" \

-H "X-API-KEY: <api-key>"

3. Review and act on findings

Each finding includes:

Code -- A stable identifier (e.g., HTML_MISSING_DOCTYPE) that never changes
Severity -- critical (blocks send), warning (should fix), info (advisory)
Category -- html, css, images, links, spam, accessibility, rendering, dark_mode, subject, tracking
Fix text -- Actionable guidance on how to resolve the issue

Severity Levels

Severity	Meaning	Send Impact
`critical`	Broken rendering or deliverability risk	Blocks send unless overridden
`warning`	Should be fixed but won't break anything	Does not block
`info`	Advisory -- best practice recommendation	Does not block

Pre-Send Blocking

When block_send_on_critical is enabled (the default), Synapse checks inspect results before every campaign send and flow activation:

No recent inspect (within 7 days for the current template version) -- send is blocked with block_no_inspect
Open critical findings -- send is blocked with block_critical
Override -- users with inspect:write permission can create a single-use override token with a required reason. The override is audit-logged.
Advisory mode -- workspaces can disable blocking via the config endpoint, making all findings informational only.

Credits

Quick Check is always free. Full Inspect consumes 1 credit per unique template version. Cache hits (re-running the same template without changes) cost 0 credits.

Plan	Monthly Credits	Overage
Free	5	Blocked on exhaustion
Starter	25	Blocked on exhaustion
Growth	100	Allowed (metered billing)
Enterprise	Unlimited	N/A

See Credits & Billing for details.

Auto-Fixers

Some findings include an auto-fix option. When available, Synapse can automatically transform your template HTML to resolve the issue. Currently supported for dark-mode meta tags, CSS color schemes, MSO overrides, and logo dark-mode swaps.

See Auto-Fixers for the full list of auto-fixable codes.

Findings Catalog

Synapse Inspect includes 110+ finding codes across 10 categories. Each code is a stable identifier that will never be reused or renumbered.

See Findings Catalog for the complete reference.