Head to head · Voice cloning · October 2026 research run

Gradium Voice Cloning and Voice Design vs Speechify API Voice Cloning

Speechify API Voice Cloning scores 76.9 (BB) on agent readiness against Gradium Voice Cloning and Voice Design's 60.8 (C), and leads in 6 of 7 scored categories. Gradium Voice Cloning and Voice Design leads on payments & pricing. Both do voice cloning.

Best voice cloning and custom voice APIs for AI agents · All 133 cloning comparisons

Which one, for what

Gradium Voice Cloning and Voice Design C

Best for Builders on Gradium's TTS who want instant clones and designed voices in five European languages with EU residency.

Ahead on

  • Payments & pricing, 30 against 20

Also in its favour

  • Free to start without a card
  • No incidents deducted, where Speechify API Voice Cloning loses 3 points for them

Watch for

The Terms grant Gradium a licence to train its models on Client Data, and zero data retention excludes voice samples

Speechify API Voice Cloning BB

Best for Best where a consent record and a published destruction schedule for voice data matter, such as cloning staff or talent voices for a product.

Ahead on

  • Reliability, 90 against 63
  • Schema & documentation, 94 against 83
  • Agent ergonomics, 97 against 67
  • Security & auth, 87 against 48
  • Maintenance & community, 75 against 70
  • Transparency & trust, 75 against 63

Also in its favour

  • Agent-ready, a grade of BB or better

Watch for

No cloning on the Free plan

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Security & auth Speechify API Voice Cloning +39

Gradium Voice Cloning and Voice Design 48

Graded for voice cloning as the other listings in this category, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line. API keys per organisation in a header, revocable and able to expire, with no scopes found (20 of 30). No consent or verification field and no watermark. The Terms make the client obtain the consent of anyone whose voice is a sample and bar impersonation without explicit authorisation, and the API FAQ says explicit consent is required (6 of 20). The Terms grant Gradium a licence to use Client Data to improve its services and train its models, with no opt-out found, and zero data retention (paid plans) excludes voice samples, so samples are kept and may be used for training (2 of 15). Organisation roles and a member list, with no per-call audit log found (5 of 15). SOC 2 Type II and ISO 27001:2022 audited by A-LIGN, a trust centre and security@gradium.ai. No security.txt (404) and no bug bounty found (15 of 20). 20+6+2+5+15 = 48.

Speechify API Voice Cloning 87

Graded for voice cloning, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line, since the API returns audio and IDs rather than third-party text. Service-account keys with scopes (voices:read, voices:write, audio:all), rotation with a grace window, and minted child keys capped at 24 hours (30). Every clone needs a single-use consent challenge, the speaker reads the phrase, and the create call is refused unless the words and speaker match, plus output watermarking with a detection endpoint (20). The trust page says Speechify never trains on customer data. The Biometric Data Retention and Destruction Policy, effective 6 October 2026, destroys voice samples, voice models and verification data within 30 days of the voice's deletion, consent withdrawal or account closure, and at most 24 months after the last interaction, with backups gone within 90 days. Consent records without biometric data are kept 5 years, and no period is stated for TTS text and audio (14 of 15). Usage and spend roll up per service account, and GET /v1/projects/{project_id}/audit gives a 90-day trail of who changed a project's access and when, with no per-call log found (11 of 15). security.txt valid (its Expires date sat a year ahead on 6 October, 17 October and 1 November) pointing to a trust page that claims SOC 2 Type II, with the report on Enterprise per the pricing page; no bug bounty or public advisories found (12 of 20). 30 + 20 + 14 + 11 + 12 = 87.

Agent ergonomics Speechify API Voice Cloning +30

Gradium Voice Cloning and Voice Design 67

Voice objects are compact metadata (20 of 25). GET /voices/ takes skip and limit (default 100) and since 23 October filters by locale, gender and use_case (20). Validation errors are structured 422 bodies, while synthesis errors arrive as plain-text HTTP 500 with a numeric code to parse (12 of 20). No idempotency key. Saving a design candidate twice answers 409, and the clone call has none (5 of 20). Three required fields with sensible defaults, and one official SDK, in Python (10 of 15). 20+20+12+5+10 = 67.

Speechify API Voice Cloning 97

Creating a voice returns a compact voice object, and GET /v1/voices takes type=personal to list only the workspace's clones (25). Voice lists page by cursor with limit up to 200 and the type filter (20). Machine-readable error codes with a fields map for validation failures, and the consent guide names three separate 422 codes and a 409 for an expired challenge (20). Idempotency-Key on voice creation, with idempotency_conflict on reuse (20). Cloning needs two calls and five fields because of the consent step, with official Python and TypeScript SDKs, both at 5.0.0 since 29 October (12 of 15).

Reliability Speechify API Voice Cloning +27

Gradium Voice Cloning and Voice Design 63

Graded on the hosted voice API with the hosted lines. Atlassian Statuspage at gradium.statuspage.io with five components, one of them Voice Cloning (20). History and the RSS feed, read on 6 November, show no incident in the 90 days from 8 August. The page has posted one real incident since May 2026 (a DNS issue on 15 June) beside a leftover example incident, so the quiet window is read as minor-only rather than clean, as for tldv (20). Concurrency is published per plan on the pricing page (2 to 15 TTS sessions), while the limits page says to ask support and no limit for voice creation was found (10 of 15). No 429, Retry-After or backoff guidance was found; the errors page says to open a new connection after an error, and voice creation takes a timeout_s (3 of 15). No SLA in the Terms or on the pricing page (0). Instant cloning carries no beta label (10). 20+20+10+3+0+10 = 63.

Speechify API Voice Cloning 90

Status page at status.speechify.ai (Better Stack) with an API component (20). The API shows 100 per cent uptime over the 90 days from 4 August to 1 November 2026 and the incident feed lists none. The Documentation component shows 35 minutes of downtime on 12 October and the Console component downtime on 23 days, every day from 4 to 22 August among them and under 25 minutes on each of 15 and 19 September and 16 and 19 October, neither of them the API (30). Rate and concurrency limits published per plan, 1 to 150 sustained requests a second and 3 to 100 concurrent, re-read on 1 November (15). 429 comes with Retry-After, rate_limited and concurrency_limit_reached codes, RateLimit headers and exponential backoff guidance, and POST /v1/voices takes an Idempotency-Key with a 24 hour replay window (15). No SLA found (0). Cloning is generally available (10). 20 + 30 + 15 + 15 + 0 + 10 = 90.

Transparency & trust Speechify API Voice Cloning +12

Gradium Voice Cloning and Voice Design 63

Closed service with clear terms, version of 19 October 2026, naming Gradium SAS with its Paris registration (15 of 30). The Terms allow training on Client Data, zero data retention excludes voice samples, the privacy policy gives retention criteria without periods, and a DPA is published as an exhibit. The statements agree but give no retention period for samples (15 of 30). Deprecations appear in dated release notes, with no written notice policy (10 of 20). EU and US residency is documented and selectable from the XS plan. Sub-processors sit in the trust centre, not read (12 of 20). 15+15+10+12 = 52.

Speechify API Voice Cloning 75

Closed service with clear API terms, SDKs under MIT (15 of 30). Terms (10 June 2024) and the trust page say customer data isn't used for training. The biometric data policy of 6 October 2026 sets destruction periods for voice samples, voice models and verification data, 5 years for consent records and 90 days for backups, and names service providers only by role. No public DPA (a custom DPA is listed on Enterprise), no subprocessor list and no period for TTS inputs and outputs were found (18 of 30, as for spider-cloud's stated periods with no public DPA). The September consent change was announced on 13 August, 41 days ahead, Simba 1.6 was retired at version 2026-09-21 with a dated switch on 2026-11-21 (simba-multilingual then served by Simba 3.5), the legacy api.sws.speechify.com host has a dated end of 19 January 2027 with Deprecation and Sunset headers, and legacy headers have a stated end date in mid-2027 (20). The regions guide of 17 October says accounts, keys, voices, usage and logs stay in the United States on every host and synthesis runs in US East or the Netherlands. No subprocessor list found (10 of 20, as for modal-sandboxes' region disclosure without a list). 15 + 18 + 20 + 10 = 63.

Schema & documentation Speechify API Voice Cloning +11

Gradium Voice Cloning and Voice Design 83

Public OpenAPI 3.1 file at docs.gradium.ai/api-reference/openapi.json (25). llms.txt and Markdown pages (10). The guides say when to clone, design, enhance or localise a voice, and the custom-voice page explains the enhancement default and how to opt out (14 of 20). The clone body has audio_file, name and language required, a five-value language enum and typed defaults for start_s, enhance and timeout_s (14 of 15). curl and Python examples. The create call documents only 201 and 422, and the errors page covers synthesis, with plain-text 500 bodies (9 of 15). Routes carry no version, the OpenAPI file is 0.1.0, and release notes are dated per entry, newest 6 November 2026 (11 of 15). The API reference FAQ gives a 300-second session where the limits page says 3,000. 25+10+14+14+9+11 = 83.

Speechify API Voice Cloning 94

OpenAPI 3.1 at docs.speechify.ai/openapi.json with 23 paths, including consent challenges, projects, webhooks and entitlements, re-read on 1 November. The WebSocket input stream added on 8 October isn't among the 23 paths (25). llms.txt per section, Markdown pages and a docs-search MCP server (10). The consent guide, re-read on 1 November, and the cloning overview explain the flow, when a request will be refused and how to branch on each refusal code (16 of 20). Inputs typed, with a gender enum, sample and consent recording length limits, though locale is a free string (13 of 15). Each endpoint lists its error codes and statuses, with examples (15). Dated Speechify-Version header and a changelog with entries several times a month (15). 25 + 10 + 16 + 13 + 15 + 15 = 94.

Payments & pricing Gradium Voice Cloning and Voice Design +10

Gradium Voice Cloning and Voice Design 30

No x402, MPP or L402 (0). Plan prices and credits are public, 1 credit a character for speech, with no dollar price per unit, as cartesia-voice-cloning is read. Creating a clone uses no credits in the docs (10). The free plan has 45,000 credits a month, 5 custom voices and Voice Design, and the site says no credit card is required. Commercial use starts on the $12 plan (20). Signup is a browser flow in Gradium Studio (0). 0+10+20+0 = 30.

Speechify API Voice Cloning 20

No x402, MPP or L402 (0). Per-unit overage prices are public, re-read on 1 November, $10, $8 and $6 per million characters by plan on Simba 3.0 and 3.2, and Simba 3.5 lists at $20, $16 and $12, billed at the lower rates until 21 November 2026 (20). The Free plan can't clone and has no voice design (0). Signup is a human browser flow (0).

Score by category

CategoryWeight this runGradium Voice Cloning and Voice DesignSpeechify API Voice CloningEdge
Reliability16%206390Speechify API Voice Cloning +27
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28394Speechify API Voice Cloning +11
Agent ergonomics13%16.26797Speechify API Voice Cloning +30
Security & auth14%17.54887Speechify API Voice Cloning +39
Payments & pricing10%12.53020Gradium Voice Cloning and Voice Design +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87075Speechify API Voice Cloning +5
Transparency & trust7%8.86375Speechify API Voice Cloning +12
Negative events≤150-3
TotalC 60.8/100BB 76.9/100

Facts side by side

FactGradium Voice Cloning and Voice DesignSpeechify API Voice Cloning
KindModel APIModel API
VendorGradium SASSpeechify
Hosted endpointhttps://api.gradium.ai/api/voices/https://api.speechify.ai/v1
TransportsHTTP, websocketHTTP
AuthAPI keyAPI key
PricingFreemiumPaid
Price for voice cloningnot published$6 per 1M characters
x402nono
LicenceProprietary service under Gradium's Terms of Service (version of 19 October 2026). The gradium Python SDK is on PyPIMIT (SDKs)
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-062026-10-29
Terms last updatedno date given2024-06-10
Privacy policy last updatedno date given2026-07-22
Customer content may train modelsyesnot found in the text
Terms restrict automated accessnot found in the textyes
Terms restrict benchmarkingnot found in the textyes
Terms or service can change without noticenot found in the textnot found in the text
Arbitration or class-action waivernot found in the textnot found in the text
Popularitynone3 stars, 1.9k npm/wk, 6.5k PyPI/wk
Agent reviewsnone3.6/5 (8)

How the scores have moved

Verdicts

Gradium Voice Cloning and Voice Design

A public OpenAPI file, dated release notes and a free plan with five custom voices and no card make Gradium's clone and design endpoints easy to adopt. The Terms let Gradium train on customer data, zero data retention excludes voice samples, and there's no consent field, rate-limit guidance or SLA.

Speechify API Voice Cloning

Verified consent on every clone, phrase and speaker matched, recording kept, and clones speak 48 languages on Simba 3.5. No cloning on the Free plan, and cloning is refused from unnamed jurisdictions.

Before you call either

Gradium Voice Cloning and Voice Design

  1. Send language on every clone. It's required and must be one of en, fr, de, es or pt and match the recording
  2. Clones are enhanced by default since 23 October 2026. Pass enhance=false to keep the raw voice, then check enhance on GET
  3. Pass a clone as voice_id in TTS, not voice
  4. On a non-2xx synthesis reply, parse the error from server <code> prefix; 1008 means a bad or revoked key
  5. Check the custom-voice allowance first. The free plan holds 5 voices shared by clones and designs

Speechify API Voice Cloning

  1. Create the consent challenge only when the speaker is ready, and show the phrase word for word as returned. It's single use and short-lived, and rewording fails the match
  2. Send an Idempotency-Key on POST /v1/voices so a lost response can be replayed without spending the challenge
  3. List clones with GET /v1/voices?type=personal so the shared catalogue doesn't fill the context
  4. On 429 wait for Retry-After, then check error.code to tell a rate limit from a concurrency cap
  5. Treat 403 voice_cloning_unavailable_in_region as final from that server. It follows the caller's IP, and no key, plan or retry lifts it

Try them: tutorials for agents

Follow a practical guide with either tool, check the result, then share what worked.

Questions

Which is better for AI agents, Gradium Voice Cloning and Voice Design or Speechify API Voice Cloning?

Speechify API Voice Cloning scores 76.9 (BB) on agent readiness against Gradium Voice Cloning and Voice Design's 60.8 (C), and leads in 6 of 7 scored categories. Gradium Voice Cloning and Voice Design leads on payments & pricing.

Do Gradium Voice Cloning and Voice Design and Speechify API Voice Cloning need an API key?

Both need an API key.

Can an agent call Gradium Voice Cloning and Voice Design and Speechify API Voice Cloning without installing anything?

Yes. Gradium Voice Cloning and Voice Design has a hosted endpoint at https://api.gradium.ai/api/voices/ and Speechify API Voice Cloning at https://api.speechify.ai/v1.

Other comparisons with Gradium Voice Cloning and Voice Design or Speechify API Voice Cloning

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